description: You are given a book with n chapters.
  
  Each chapter has a specified list of other chapters that need to be understood in order to understand this chapter. To understand a chapter, you must read it after you understand every chapter on its required list.
  
  Currently you don't understand any of the chapters. You are going to read the book from the beginning till the end repeatedly until you understand the whole book. Note that if you read a chapter at a moment when you don't understand some of the required chapters, you don't understand this chapter.
  
  Determine how many times you will read the book to understand every chapter, or determine that you will never understand every chapter no matter how many times you read the book.
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 2⋅10^4).
  
  The first line of each test case contains a single integer n (1 ≤ n ≤ 2⋅10^5) — number of chapters.
  
  Then n lines follow. The i-th line begins with an integer k_i (0 ≤ k_i ≤ n-1) — number of chapters required to understand the i-th chapter. Then k_i integers a_{i,1}, a_{i,2}, ..., a_{i, k_i} (1 ≤ a_{i, j} ≤ n, a_{i, j} ≠ i, a_{i, j} ≠ a_{i, l} for j ≠ l) follow — the chapters required to understand the i-th chapter.
  
  It is guaranteed that the sum of n and sum of k_i over all testcases do not exceed 2⋅10^5.
  
  Output
  
  For each test case, if the entire book can be understood, print how many times you will read it, otherwise print -1.
  
  Example
  
  Input
  
  
  5
  4
  1 2
  0
  2 1 4
  1 2
  5
  1 5
  1 1
  1 2
  1 3
  1 4
  5
  0
  0
  2 1 2
  1 2
  2 2 1
  4
  2 2 3
  0
  0
  2 3 2
  5
  1 2
  1 3
  1 4
  1 5
  0
  
  
  Output
  
  
  2
  -1
  1
  2
  5
  
  Note
  
  In the first example, we will understand chapters \{2, 4\} in the first reading and chapters \{1, 3\} in the second reading of the book.
  
  In the second example, every chapter requires the understanding of some other chapter, so it is impossible to understand the book.
  
  In the third example, every chapter requires only chapters that appear earlier in the book, so we can understand everything in one go.
  
  In the fourth example, we will understand chapters \{2, 3, 4\} in the first reading and chapter 1 in the second reading of the book.
  
  In the fifth example, we will understand one chapter in every reading from 5 to 1.
solution: from collections import defaultdict, Counter, deque
  from math import sqrt, log10, log, floor, factorial, gcd
  from bisect import bisect_left, bisect_right
  from itertools import permutations, combinations
  import sys, io, os
  input = sys.stdin.readline
  # input=io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
  # sys.setrecursionlimit(10000)
  inf = float('inf')
  mod = 10 ** 9 + 7
  def yn(a): print("YES" if a else "NO")
  ceil = lambda a, b: (a + b - 1) // b
  class SortedList:
      def __init__(self, iterable=[], _load=200):
          """Initialize sorted list instance."""
          values = sorted(iterable)
          self._len = _len = len(values)
          self._load = _load
          self._lists = _lists = [values[i:i + _load] for i in range(0, _len, _load)]
          self._list_lens = [len(_list) for _list in _lists]
          self._mins = [_list[0] for _list in _lists]
          self._fen_tree = []
          self._rebuild = True
  
      def _fen_build(self):
          """Build a fenwick tree instance."""
          self._fen_tree[:] = self._list_lens
          _fen_tree = self._fen_tree
          for i in range(len(_fen_tree)):
              if i | i + 1 < len(_fen_tree):
                  _fen_tree[i | i + 1] += _fen_tree[i]
          self._rebuild = False
  
      def _fen_update(self, index, value):
          """Update `fen_tree[index] += value`."""
          if not self._rebuild:
              _fen_tree = self._fen_tree
              while index < len(_fen_tree):
                  _fen_tree[index] += value
                  index |= index + 1
  
      def _fen_query(self, end):
          """Return `sum(_fen_tree[:end])`."""
          if self._rebuild:
              self._fen_build()
  
          _fen_tree = self._fen_tree
          x = 0
          while end:
              x += _fen_tree[end - 1]
              end &= end - 1
          return x
  
      def _fen_findkth(self, k):
          """Return a pair of (the largest `idx` such that `sum(_fen_tree[:idx]) <= k`, `k - sum(_fen_tree[:idx])`)."""
          _list_lens = self._list_lens
          if k < _list_lens[0]:
              return 0, k
          if k >= self._len - _list_lens[-1]:
              return len(_list_lens) - 1, k + _list_lens[-1] - self._len
          if self._rebuild:
              self._fen_build()
  
          _fen_tree = self._fen_tree
          idx = -1
          for d in reversed(range(len(_fen_tree).bit_length())):
              right_idx = idx + (1 << d)
              if right_idx < len(_fen_tree) and k >= _fen_tree[right_idx]:
                  idx = right_idx
                  k -= _fen_tree[idx]
          return idx + 1, k
  
      def _delete(self, pos, idx):
          """Delete value at the given `(pos, idx)`."""
          _lists = self._lists
          _mins = self._mins
          _list_lens = self._list_lens
  
          self._len -= 1
          self._fen_update(pos, -1)
          del _lists[pos][idx]
          _list_lens[pos] -= 1
  
          if _list_lens[pos]:
              _mins[pos] = _lists[pos][0]
          else:
              del _lists[pos]
              del _list_lens[pos]
              del _mins[pos]
              self._rebuild = True
  
      def _loc_left(self, value):
          """Return an index pair that corresponds to the first position of `value` in the sorted list."""
          if not self._len:
              return 0, 0
  
          _lists = self._lists
          _mins = self._mins
  
          lo, pos = -1, len(_lists) - 1
          while lo + 1 < pos:
              mi = (lo + pos) >> 1
              if value <= _mins[mi]:
                  pos = mi
              else:
                  lo = mi
  
          if pos and value <= _lists[pos - 1][-1]:
              pos -= 1
  
          _list = _lists[pos]
          lo, idx = -1, len(_list)
          while lo + 1 < idx:
              mi = (lo + idx) >> 1
              if value <= _list[mi]:
                  idx = mi
              else:
                  lo = mi
  
          return pos, idx
  
      def _loc_right(self, value):
          """Return an index pair that corresponds to the last position of `value` in the sorted list."""
          if not self._len:
              return 0, 0
  
          _lists = self._lists
          _mins = self._mins
  
          pos, hi = 0, len(_lists)
          while pos + 1 < hi:
              mi = (pos + hi) >> 1
              if value < _mins[mi]:
                  hi = mi
              else:
                  pos = mi
  
          _list = _lists[pos]
          lo, idx = -1, len(_list)
          while lo + 1 < idx:
              mi = (lo + idx) >> 1
              if value < _list[mi]:
                  idx = mi
              else:
                  lo = mi
  
          return pos, idx
  
      def add(self, value):
          """Add `value` to sorted list."""
          _load = self._load
          _lists = self._lists
          _mins = self._mins
          _list_lens = self._list_lens
  
          self._len += 1
          if _lists:
              pos, idx = self._loc_right(value)
              self._fen_update(pos, 1)
              _list = _lists[pos]
              _list.insert(idx, value)
              _list_lens[pos] += 1
              _mins[pos] = _list[0]
              if _load + _load < len(_list):
                  _lists.insert(pos + 1, _list[_load:])
                  _list_lens.insert(pos + 1, len(_list) - _load)
                  _mins.insert(pos + 1, _list[_load])
                  _list_lens[pos] = _load
                  del _list[_load:]
                  self._rebuild = True
          else:
              _lists.append([value])
              _mins.append(value)
              _list_lens.append(1)
              self._rebuild = True
  
      def discard(self, value):
          """Remove `value` from sorted list if it is a member."""
          _lists = self._lists
          if _lists:
              pos, idx = self._loc_right(value)
              if idx and _lists[pos][idx - 1] == value:
                  self._delete(pos, idx - 1)
  
      def remove(self, value):
          """Remove `value` from sorted list; `value` must be a member."""
          _len = self._len
          self.discard(value)
          if _len == self._len:
              raise ValueError('{0!r} not in list'.format(value))
  
      def pop(self, index=-1):
          """Remove and return value at `index` in sorted list."""
          pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
          value = self._lists[pos][idx]
          self._delete(pos, idx)
          return value
  
      def bisect_left(self, value):
          """Return the first index to insert `value` in the sorted list."""
          pos, idx = self._loc_left(value)
          return self._fen_query(pos) + idx
  
      def bisect_right(self, value):
          """Return the last index to insert `value` in the sorted list."""
          pos, idx = self._loc_right(value)
          return self._fen_query(pos) + idx
  
      def count(self, value):
          """Return number of occurrences of `value` in the sorted list."""
          return self.bisect_right(value) - self.bisect_left(value)
  
      def __len__(self):
          """Return the size of the sorted list."""
          return self._len
  
      def __getitem__(self, index):
          """Lookup value at `index` in sorted list."""
          pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
          return self._lists[pos][idx]
  
      def __delitem__(self, index):
          """Remove value at `index` from sorted list."""
          pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
          self._delete(pos, idx)
  
      def __contains__(self, value):
          """Return true if `value` is an element of the sorted list."""
          _lists = self._lists
          if _lists:
              pos, idx = self._loc_left(value)
              return idx < len(_lists[pos]) and _lists[pos][idx] == value
          return False
  
      def __iter__(self):
          """Return an iterator over the sorted list."""
          return (value for _list in self._lists for value in _list)
  
      def __reversed__(self):
          """Return a reverse iterator over the sorted list."""
          return (value for _list in reversed(self._lists) for value in reversed(_list))
  
      def __repr__(self):
          """Return string representation of sorted list."""
          return 'SortedList({0})'.format(list(self))
  import os
  import sys
  from io import BytesIO, IOBase
  
  BUFSIZE = 8192
  
  
  class FastIO(IOBase):
      newlines = 0
  
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
  
      def read(self):
          while True:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
  
      def readline(self):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
  
      def flush(self):
          if self.writable:
              os.write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
  
  
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
  
  
  sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip("\r\n")
  
  t=int(input())
  for test in range(1,t+1):
      n=int(input())
      those_ahead=[[] for i in range(n)]
      indegree=[ 0 for i in range(n)]
      s=SortedList()
      for i in range(n):
          _,*k=[int(ii)-1 for ii in input().split()]
          for j in k:
              those_ahead[j].append(i)
          indegree[i]=len(k)
          if indegree[i]==0:
              s.add(i)
  
      counter=0
      visited=set()
      for i in range(n):
          counter+=1
          start=-1
          while s:
              indexa=s.bisect_right(start)
              if indexa==len(s):
                  break
              start=s.pop(indexa)
              visited.add(start)
              # print(f"index {start}")
              for iterate in those_ahead[start]:
                  indegree[iterate]-=1
                  if indegree[iterate]==0:
                      s.add(iterate)
          # print("loop end")
          if start==-1:
              counter-=1
              break
      if len(visited)==n:
          print(counter)
      else:
          print(-1)