#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void upmax(T& a, T b) {
  if (a < b) a = b;
}
template <class T>
inline void upmin(T& a, T b) {
  if (a > b) a = b;
}
const int maxn = 1003;
const int maxm = 200007;
const int mod = 1000000007;
const int inf = 0x7fffffff;
const double eps = 1e-7;
typedef int arr[maxn];
typedef int adj[maxm];
inline int fcmp(double a, double b) {
  if (fabs(a - b) <= eps) return 0;
  if (a < b - eps) return -1;
  return 1;
}
inline int add(int a, int b) { return ((long long)a + b) % mod; }
inline int mul(int a, int b) { return ((long long)a * b) % mod; }
inline int dec(int a, int b) { return add(a, mod - b % mod); }
inline int Pow(int a, int b) {
  int t = 1;
  while (b) {
    if (b & 1) t = mul(t, a);
    a = mul(a, a), b >>= 1;
  }
  return t;
}
template <typename Type>
inline Type RD() {
  char c = getchar();
  Type x = 0, flag = 1;
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    flag = -1;
  else
    x = c - '0';
  while (isdigit(c = getchar())) x = x * 10 + c - '0';
  return x * flag;
}
inline char rdch() {
  char c = getchar();
  while (!isalpha(c)) c = getchar();
  return c;
}
int n, m, tot;
arr cnt, gift_cnt;
pair<int, int> gift[maxn];
long double a[maxn], k[maxn], f[maxn][maxn];
void input() {
  n = RD<int>(), m = RD<int>();
  for (int i = 1, _ = m; i <= _; i++) {
    cnt[i] = RD<int>();
    for (int j = 1, _ = cnt[i]; j <= _; j++)
      gift[++tot] = make_pair(RD<int>(), i);
  }
  sort(gift + 1, gift + tot + 1);
}
inline int get_pre(int i) {
  while (i > 1 && gift[i - 1].first == gift[i].first) i--;
  return i;
}
void solve() {
  long double tot_p = 1.0;
  int st = 0, ed = -1;
  for (int i = tot; i;) {
    int j = get_pre(i);
    if (i - j + 1 > n) {
      st = j, ed = i;
      break;
    }
    do {
      int u = gift[i--].second;
      n--;
      assert(cnt[u] != gift_cnt[u]);
      tot_p *= (gift_cnt[u] + 1.0) / (cnt[u] - gift_cnt[u]);
      gift_cnt[u]++;
    } while (i >= j);
  }
  int len = ed - st + 1;
  for (int i = 1, _ = len; i <= _; i++) {
    int u = gift[i + st - 1].second;
    k[i] = cnt[u], a[i] = gift_cnt[u];
  }
  f[0][0] = tot_p;
  for (int i = 1, _ = len; i <= _; i++)
    for (int j = 0, _ = i; j <= _; j++) {
      if (j) f[i][j] += f[i - 1][j - 1] * (a[i] + 1.0) / (k[i] - a[i]) * j / i;
      f[i][j] += f[i - 1][j] * (i - j) / i;
    }
  printf("%.9lf\n", (double)f[len][n]);
}
int main() {
  input();
  solve();
  return 0;
}
