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: import java.io.*;
  import java.util.*;
  
  
  
  import java.math.*;
  import java.math.BigInteger;
  
  
  public final class A
  {    
  	static PrintWriter out = new PrintWriter(System.out); 
  	static StringBuilder ans=new StringBuilder();
  	static FastReader in=new FastReader();
  	static ArrayList<Integer> g[];
  	static long mod=(long)998244353,INF=Long.MAX_VALUE;
  	static boolean set[],col[]; 
  	static int par[],tot[],partial[];
  	static int Days[],P[][];
  	static int dp[][],sum=0,size[];
  	static int seg[];
  	static ArrayList<Long> A;
  	//	static HashSet<Integer> set;
  	//	static node1 seg[];
  	//static pair moves[]= {new pair(-1,0),new pair(1,0), new pair(0,-1), new pair(0,1)};
  	public static void main(String args[])throws IOException
  	{		
  		int T=i();
  		outer:while(T-->0)
  		{
  			int N=i();
  			setGraph(N);
  			for(int i=1; i<=N; i++)
  			{
  				int k=i();
  				while(k-->0)
  				{
  					g[i].add(i());
  				}
  				//System.out.println(g[i]);
  			}
  			int max=0;
  			cycle=false;
  			for(int i=1; i<=N; i++)
  			{
  				cycle=false;
  				int a=f(i);
  				//print(Days);
  				if(cycle)
  				{
  					max=-1;
  					break;
  				}
  				max=Math.max(max,a);
  			}
  		//	print(Days);
  			ans.append(max+"\n");
  		}
  		out.println(ans);
  		out.close();
  	}
  	static boolean cycle=false;
  	static int f(int n)
  	{
  		if(set[n])return Days[n];
  		set[n]=true;
  		int max=1;
  		for(int x:g[n])
  		{
  			if(set[x] && Days[x]==-1)
  			{
  				cycle=true;
  				return -1;
  			}
  			if(!set[x])
  			{
  				f(x);
  			}
  			if(x<n)max=Math.max(max, Days[x]);
  			else max=Math.max(max, Days[x]+1);
  		}
  		return Days[n]=max;
  	}
  	static int index(int a,ArrayList<Integer> A)
  	{
  		int l=-1,r=A.size();
  		while(r-l>1)
  		{
  			int m=(l+r)/2;
  			int x=A.get(m);
  			if(x<=a)l=m;
  			else r=m;
  		}
  		return r;
  	}
  	static long and(int i,int j)
  	{
  		System.out.println("and "+i+" "+j);
  		return l();
  	}
  	static long or(int i,int j)
  	{
  		System.out.println("or "+i+" "+j);
  		return l();
  	}
  	static boolean is_Sorted(int A[])
  	{
  		int N=A.length;
  		for(int i=1; i<=N; i++)if(A[i-1]!=i)return false;
  		return true;
  	}
  	static boolean f(StringBuilder sb,String Y,String order)
  	{
  		StringBuilder res=new StringBuilder(sb.toString());
  		HashSet<Character> set=new HashSet<>();
  		for(char ch:order.toCharArray())
  		{
  			set.add(ch);
  			for(int i=0; i<sb.length(); i++)
  			{
  				char x=sb.charAt(i);
  				if(set.contains(x))continue;
  				res.append(x);
  			}
  		}
  
  		String str=res.toString();
  		return str.equals(Y);
  	}
  	static boolean all_Zero(int f[])
  	{
  		for(int a:f)if(a!=0)return false;
  		return true;
  	}
  	static long form(int a,int l)
  	{
  		long x=0;
  		while(l-->0)
  		{
  			x*=10;
  			x+=a;
  		}
  		return x;
  	}
  	static int count(String X)
  	{
  		HashSet<Integer> set=new HashSet<>();
  		for(char x:X.toCharArray())set.add(x-'0');
  		return set.size();
  	}
  
  	
  	//	static void build(int v,int tl,int tr,long A[])
  	//	{
  	//		if(tl==tr)
  	//		{
  	//			seg[v]=A[tl];
  	//		}
  	//		else
  	//		{
  	//			int tm=(tl+tr)/2;
  	//			build(v*2,tl,tm,A);
  	//			build(v*2+1,tm+1,tr,A);
  	//			seg[v]=Math.min(seg[v*2], seg[v*2+1]);
  	//		}
  	//	}
  	static long ask(int v,int tl,int tr,int l,int r)
  	{
  		if(l>r)return (long)(1e10);
  		if(tl==l && tr==r)
  		{
  			return seg[v];
  		}
  		int tm=(tl+tr)/2;
  		return Math.min(ask(v*2,tl,tm,l,Math.min(tm, r)), ask(v*2+1,tm+1,tr,Math.max(l,tm+1),r));
  	}
  	static int [] sub(int A[],int B[])
  	{
  		int N=A.length;
  		int f[]=new int[N];
  		for(int i=N-1; i>=0; i--)
  		{
  			if(B[i]<A[i])
  			{
  				B[i]+=26;
  				B[i-1]-=1;
  			}
  			f[i]=B[i]-A[i];
  		}
  		for(int i=0; i<N; i++)
  		{
  			if(f[i]%2!=0)f[i+1]+=26;
  			f[i]/=2;
  		}
  		return f;
  	}
  	
  
  
  
  
  	static int max(int a ,int b,int c,int d)
  	{
  		a=Math.max(a, b);
  		c=Math.max(c,d);
  		return Math.max(a, c);
  	}
  	static int min(int a ,int b,int c,int d)
  	{
  		a=Math.min(a, b);
  		c=Math.min(c,d);
  		return Math.min(a, c);
  	}
  
  
  
  	static HashMap<Integer,Integer> Hash(int A[])
  	{
  		HashMap<Integer,Integer> mp=new HashMap<>();
  		for(int a:A)
  		{
  			int f=mp.getOrDefault(a,0)+1;
  			mp.put(a, f);
  		}
  		return mp;
  	}
  	static long mul(long a, long b)
  	{
  		return ( a %mod * 1L * b%mod )%mod;
  	}
  	static void swap(int A[],int a,int b)
  	{
  		int t=A[a];
  		A[a]=A[b];
  		A[b]=t;
  	}
  
  
  	static int find(int a)
  	{
  		if(par[a]<0)return a;
  		return par[a]=find(par[a]);
  	}
  	static void union(int a,int b)
  	{
  		a=find(a);
  		b=find(b);
  		if(a!=b)
  		{
  			par[a]+=par[b];
  			par[b]=a;
  		}
  	}
  	static boolean isSorted(int A[])
  	{
  		for(int i=1; i<A.length; i++)
  		{
  			if(A[i]<A[i-1])return false;
  		}
  		return true;
  	}
  
  	static boolean isDivisible(StringBuilder X,int i,long num)
  	{
  		long r=0;
  		for(; i<X.length(); i++)
  		{
  			r=r*10+(X.charAt(i)-'0');
  			r=r%num;
  		}
  		return r==0;
  	}    
  
  
  
  	static int lower_Bound(int A[],int low,int high, int x) 
  	{ 
  		if (low > high) 
  			if (x >= A[high]) 
  				return A[high]; 
  
  		int mid = (low + high) / 2; 
  
  		if (A[mid] == x) 
  			return A[mid]; 
  
  		if (mid > 0 && A[mid - 1] <= x && x < A[mid]) 
  			return A[mid - 1]; 
  
  		if (x < A[mid]) 
  			return lower_Bound( A, low, mid - 1, x); 
  
  		return lower_Bound(A, mid + 1, high, x); 
  	} 
  
  	static String f(String A)
  	{
  		String X="";
  		for(int i=A.length()-1; i>=0; i--)
  		{
  			int c=A.charAt(i)-'0';
  			X+=(c+1)%2;
  		}
  		return X;
  	}
  
  	static void sort(long[] a) //check for long
  	{
  		ArrayList<Long> l=new ArrayList<>();
  		for (long i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
  
  	static String swap(String X,int i,int j)
  	{
  		char ch[]=X.toCharArray();
  		char a=ch[i];
  		ch[i]=ch[j];
  		ch[j]=a;
  		return new String(ch);
  	}
  
  	static int sD(long n)  
  	{  
  
  		if (n % 2 == 0 )  
  			return 2;  
  
  		for (int i = 3; i * i <= n; i += 2) {  
  			if (n % i == 0 )  
  				return i;  
  		}  
  
  		return (int)n;  
  	}  
  
  	static void setGraph(int N)
  	{
  		tot=new int[N+1];
  		partial=new int[N+1];
  		Days=new int[N+1];
  		P=new int[N+1][(int)(Math.log(N)+10)];
  		set=new boolean[N+1];
  		g=new ArrayList[N+1];
  		for(int i=0; i<=N; i++)
  		{
  
  			g[i]=new ArrayList<>();		
  			Days[i]=-1;
  			//D2[i]=INF;
  		}
  	}
  
  
  
  	static  long pow(long a,long b)
  	{
  		//long mod=1000000007;
  		long pow=1;
  		long x=a;
  		while(b!=0)
  		{
  			if((b&1)!=0)pow=(pow*x)%mod;
  			x=(x*x)%mod;
  			b/=2;
  		}
  		return pow;
  	}
  
  	static long toggleBits(long x)//one's complement || Toggle bits
  	{
  		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;
  
  		return ((1<<n)-1)^x;
  	}
  
  	static int countBits(long a)
  	{
  		return (int)(Math.log(a)/Math.log(2)+1);
  	}
  
  	static long fact(long N)
  	{ 
  		long n=2; 
  		if(N<=1)return 1;
  		else
  		{
  			for(int i=3; i<=N; i++)n=(n*i)%mod;
  		}
  		return n;
  	}
  
  	static int kadane(int A[])
  	{
  		int lsum=A[0],gsum=A[0];
  		for(int i=1; i<A.length; i++)
  		{
  			lsum=Math.max(lsum+A[i],A[i]);
  			gsum=Math.max(gsum,lsum);
  		}
  		return gsum;
  	}
  
  	static void sort(int[] a) {
  		ArrayList<Integer> l=new ArrayList<>();
  		for (int i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
  
  	static boolean isPrime(long N)
  	{
  		if (N<=1)  return false; 
  		if (N<=3)  return true; 
  		if (N%2 == 0 || N%3 == 0) return false; 
  		for (int i=5; i*i<=N; i=i+6) 
  			if (N%i == 0 || N%(i+2) == 0) 
  				return false; 
  		return true; 
  	}
  	static void print(char A[])
  	{
  		for(char c:A)System.out.print(c+" ");
  		System.out.println();
  	}
  	static void print(boolean A[])
  	{
  		for(boolean c:A)System.out.print(c+" ");
  		System.out.println();
  	}
  	static void print(int A[])
  	{
  		for(int a:A)System.out.print(a+" ");
  		System.out.println();	
  	}
  	static void print(long A[])
  	{
  		for(long i:A)System.out.print(i+ " ");
  		System.out.println();
  
  	}
  	static void print(boolean A[][])
  	{
  		for(boolean a[]:A)print(a);
  	}
  	static void print(long A[][])
  	{
  		for(long a[]:A)print(a);
  	}
  	static void print(int A[][])
  	{
  		for(int a[]:A)print(a);
  	}
  	static void print(ArrayList<Integer> A)
  	{
  		for(int a:A)System.out.print(a+" ");
  		System.out.println();
  	}
  
  	static int i()
  	{
  		return in.nextInt();
  	}
  
  	static long l()
  	{
  		return in.nextLong();
  	}
  
  	static int[] input(int N){
  		int A[]=new int[N];
  		for(int i=0; i<N; i++)
  		{
  			A[i]=in.nextInt();
  		}
  		return A;
  	}
  
  	static long[] inputLong(int N)     {
  		long A[]=new long[N];
  		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
  		return A;
  	}
  
  	static long GCD(long a,long b) 
  	{
  		if(b==0)
  		{
  			return a;
  		}
  		else return GCD(b,a%b );
  	}
  
  }
  class Pair implements Comparable<Pair>
  {
  	long a;
  	int index;
  	Pair(long a,int index)
  	{
  		this.index=index;
  		this.a=a;
  	}
  	public int compareTo(Pair x)
  	{
  		if(this.a==x.a)return x.index-this.index;
  		if(this.a>x.a)return 1;
  		else return -1;
  	}
  }
  
  
  //Code For FastReader
  //Code For FastReader
  //Code For FastReader
  //Code For FastReader
  class FastReader
  {
  	BufferedReader br;
  	StringTokenizer st;
  	public FastReader()
  	{
  		br=new BufferedReader(new InputStreamReader(System.in));
  	}
  
  	String next()
  	{
  		while(st==null || !st.hasMoreElements())
  		{
  			try
  			{
  				st=new StringTokenizer(br.readLine());
  			}
  			catch(IOException e)
  			{
  				e.printStackTrace();
  			}
  		}
  		return st.nextToken();
  	}
  
  	int nextInt()
  	{
  		return Integer.parseInt(next());
  	}
  
  	long nextLong()
  	{
  		return Long.parseLong(next());
  	}
  
  	double nextDouble()
  	{
  		return Double.parseDouble(next());
  	}
  
  	String nextLine()
  	{
  		String str="";
  		try
  		{
  			str=br.readLine();
  		}
  		catch (IOException e)
  		{
  			e.printStackTrace();
  		}
  		return str;
  	}
  
  }