#include <bits/stdc++.h>
using namespace std;
const long long MXN = 2e3 + 10;
const long long MXM = (1LL << 18) + 10;
const long long MX5 = 2e5 + 10;
const long long MX6 = 1e6 + 10;
const long long LOG = 20;
const long long INF = 8e18;
const double eps = 1e-9;
const long long MOD = 1e9 + 7;
long long power(long long a, long long b, long long md) {
  return (!b ? 1
             : (b & 1 ? a * power(a * a % md, b / 2, md) % md
                      : power(a * a % md, b / 2, md) % md));
}
long long bmm(long long a, long long b) {
  return (a % b == 0 ? b : bmm(b, a % b));
}
string base2(long long n) {
  string a = "";
  while (n >= 2) {
    a += (char)(n % 2 + '0');
    n /= 2;
  }
  a += (char)(n + '0');
  reverse((a).begin(), (a).end());
  return a;
}
long long n, m, t, last, p, fir, f = 1, y = 0;
double cnst = 1.0, ans = 1.0, dp[MXN][MXN];
long long K[MXN], cnt[MXN];
vector<long long> P[MXN];
vector<pair<long long, long long> > vec;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(12);
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> K[i];
    for (int j = 0; j < K[i]; j++) {
      long long x;
      cin >> x;
      P[i].push_back(x), vec.push_back({x, i}), t++;
    }
  }
  sort(((vec)).begin(), ((vec)).end());
  last = vec[t - n].first;
  for (int i = t - 1; i >= 0; i--) {
    long long id = vec[i].second;
    if (vec[i].first > last) {
      cnst *= (cnt[id] + 1.0) / (K[id] - cnt[id] + 0.0);
      cnt[id]++;
    } else if (vec[i].first == last) {
      p = i;
      if (f) {
        fir = i;
        f = 0;
      }
    }
  }
  dp[p][0] = 1.0;
  for (int i = p + 1, y = 1; i <= fir + 1; i++, y++) {
    for (int j = 0; j <= i - p; j++) {
      long long id = vec[i - 1].second;
      if (j) {
        dp[i][j] = dp[i - 1][j - 1] * (cnt[id] + 1.0) /
                       (K[id] - cnt[id] + 0.0) * (j + 0.0) / (y + 0.0) +
                   dp[i - 1][j] * (y - j + 0.0) / (y + 0.0);
      } else {
        dp[i][j] = dp[i - 1][j] * (y - j + 0.0) / (y + 0.0);
      }
    }
  }
  cout << cnst * dp[fir + 1][n - (t - p - (fir - p + 1))];
  return 0;
}
