#include <bits/stdc++.h>
using namespace std;
ifstream in("in.txt");
ofstream out("out.txt");
long long a[1000006], b[1000006];
long long fortza(long long n, long long put) {
  if (!put) return 1;
  if (put == 1) return n;
  if (put & 1) return (fortza((n * n) % 998244353, put / 2) * n) % 998244353;
  return fortza((n * n) % 998244353, put / 2) % 998244353;
}
int main() {
  long long n, k, i, j, x;
  cin >> n;
  for (i = 1; i <= n; ++i) {
    cin >> k;
    for (j = 1; j <= k; ++j) {
      cin >> x;
      b[x] = (b[x] + fortza((k * n) % 998244353, 998244353 - 2)) % 998244353;
      ++a[x];
    }
  }
  n = fortza(n, 998244353 - 2);
  for (i = 1, x = 0; i <= 1000006 - 6; ++i)
    x = (x + (a[i] * ((n * b[i]) % 998244353)) % 998244353) % 998244353;
  cout << x;
  return 0;
}
