#include <bits/stdc++.h>
using namespace std;
const int iinf = 1e9 + 7;
const long long linf = 1ll << 60;
const double dinf = 1e10;
template <typename T>
inline void scf(T &x) {
  bool f = 0;
  x = 0;
  char c = getchar();
  while ((c < '0' || c > '9') && c != '-') c = getchar();
  if (c == '-') {
    f = 1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = x * 10 + c - '0';
    c = getchar();
  }
  if (f) x = -x;
  return;
}
template <typename T1, typename T2>
void scf(T1 &x, T2 &y) {
  scf(x);
  return scf(y);
}
template <typename T1, typename T2, typename T3>
void scf(T1 &x, T2 &y, T3 &z) {
  scf(x);
  scf(y);
  return scf(z);
}
template <typename T1, typename T2, typename T3, typename T4>
void scf(T1 &x, T2 &y, T3 &z, T4 &w) {
  scf(x);
  scf(y);
  scf(z);
  return scf(w);
}
const int N = 1010;
using lflt = long double;
int n, m;
vector<int> all[N];
map<int, vector<int> > M;
int chs[N];
lflt dp[N][N];
bool f[N];
lflt C[N][N];
void solve() {
  dp[0][0] = 1.0;
  for (int i = 0; i < (m); i++) {
    int sz = (int)all[i + 1].size(), cs = chs[i + 1];
    if (f[i + 1]) {
      dp[i + 1][0] = dp[i][0] / C[sz][cs];
      for (int j = (1); j <= (n); j++) {
        dp[i + 1][j] = dp[i][j] / C[sz][cs] + dp[i][j - 1] / C[sz][cs + 1];
      }
    } else
      for (int j = (0); j <= (n); j++) dp[i + 1][j] = dp[i][j] / C[sz][cs];
  }
  return;
}
int main() {
  scf(n, m);
  for (int i = (1); i <= (m); i++) {
    int x;
    scf(x);
    while (x--) {
      int y;
      scf(y);
      all[i].push_back(y);
      if (M.find(y) == M.end()) M[y];
      M[y].push_back(i);
    }
  }
  auto it = M.end();
  while (it != M.begin()) {
    it--;
    if (n < (int)it->second.size()) break;
    for (auto x : it->second) chs[x]++;
    n -= (int)it->second.size();
  }
  C[0][0] = 1.0;
  for (int i = (1); i <= (1000); i++) {
    C[i][0] = C[i][i] = 1.0;
    for (int j = (1); j <= (i - 1); j++)
      C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
  }
  for (int x : it->second) f[x] = 1;
  solve();
  lflt ans = dp[m][n] / C[(int)it->second.size()][n];
  printf("%.15e\n", (double)ans);
  return 0;
}
