#include <bits/stdc++.h>
using namespace std;
void solve();
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed;
  cout.precision(20);
  solve();
  return 0;
}
template <typename T>
void chmin(T& a, T b) {
  if (a > b) a = b;
}
template <typename T>
void chmax(T& a, T b) {
  if (a < b) a = b;
}
template <typename T>
void MACRO_rdv2_Init(int n, T& t) {
  t.resize(n);
}
template <typename First, typename... Rest>
void MACRO_rdv2_Init(int n, First& first, Rest&... rest) {
  first.resize(n);
  MACRO_rdv2_Init(n, rest...);
}
template <typename T>
void MACRO_rdv2_Scan(int p, T& t) {
  std::cin >> t[p];
}
template <typename First, typename... Rest>
void MACRO_rdv2_Scan(int p, First& first, Rest&... rest) {
  std::cin >> first[p];
  MACRO_rdv2_Scan(p, rest...);
}
template <typename T>
void wrv(const vector<T>& v) {
  for (int(__ii) = (0); (__ii) < (((int)v.size())); ++(__ii)) {
    if (__ii) cout << ' ';
    cout << v[__ii];
  }
  cout << '\n';
}
template <typename T>
void wrm(const vector<vector<T>>& v) {
  for (int(__ii) = (0); (__ii) < (((int)v.size())); ++(__ii)) {
    for (int(__jj) = (0); (__jj) < (v[__ii].size()); ++(__jj)) {
      if (__jj) cout << ' ';
      cout << v[__ii][__jj];
    }
    cout << '\n';
  }
}
template <typename T>
void sc(T& x) {
  cin >> x;
}
template <typename Head, typename... Tail>
void sc(Head& head, Tail&... tail) {
  cin >> head;
  sc(tail...);
}
template <typename T>
void wr(const T& x) {
  cout << x << '\n';
}
template <typename Head, typename... Tail>
void wr(const Head& head, const Tail&... tail) {
  cout << head << ' ';
  wr(tail...);
}
template <typename T>
void wrf(const T& x) {
  cout << x << endl;
}
template <typename Head, typename... Tail>
void wrf(const Head& head, const Tail&... tail) {
  cout << head << ' ';
  wrf(tail...);
}
template <typename T>
void debug_out(const T& x) {
  cerr << x << '\n';
}
template <typename Head, typename... Tail>
void debug_out(const Head& head, const Tail&... tail) {
  cerr << head << ' ';
  debug_out(tail...);
}
template <typename... T>
void err(const T&... cod) {
  wr(cod...);
  exit(0);
}
const int mod = 998244353;
void add_self(int& x, int y) {
  x += y;
  if (x >= mod) x -= mod;
}
void sub_self(int& x, int y) {
  x -= y;
  if (x < 0) x += mod;
}
int add(int x, int y) {
  x += y;
  if (x >= mod) x -= mod;
  return x;
}
int sub(int x, int y) {
  x -= y;
  if (x < 0) x += mod;
  return x;
}
int powmod(long long a, long long b) {
  long long res = 1;
  a %= mod;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res % mod;
}
int mult(int x, int y) { return (1LL * x * y) % mod; }
int inv(int x) { return powmod(x, mod - 2); }
int divide(int x, int y) { return mult(x, inv(y)); }
void solve() {
  int n;
  sc(n);
  const int N = 1e6 + 10;
  vector<int> cnt(N, 0);
  vector<vector<int>> a(n);
  for (int(i) = (0); (i) < (n); ++(i)) {
    int k;
    sc(k);
    a[i].resize(k);
    for (int(j) = (0); (j) < (k); ++(j)) {
      cin >> a[i][j];
      ++cnt[a[i][j]];
    }
  }
  int ans = 0;
  for (int(i) = (0); (i) < (n); ++(i)) {
    for (int(j) = (0); (j) < (((int)a[i].size())); ++(j)) {
      int cur = divide(1, n);
      cur = mult(cur, divide(1, ((int)a[i].size())));
      cur = mult(cur, divide(cnt[a[i][j]], n));
      add_self(ans, cur);
    }
  }
  wr(ans);
}
