#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  double n, m;
  cin >> n >> m;
  vector<bool> x(n, false), y(n, false);
  int a = n, b = n;
  for (int i = 0; i < m; ++i) {
    int v, w;
    cin >> v >> w;
    --v;
    --w;
    if (!x[v]) --a;
    x[v] = true;
    if (!y[w]) --b;
    y[w] = true;
  }
  vector<vector<double> > dp(n + 1, vector<double>(n + 1));
  for (double i = 0; i <= n; ++i) {
    for (double j = 0; j <= n; ++j) {
      if (i == 0 && j == 0) dp[i][j] = 0;
      if (i == 0 && j != 0) dp[i][j] = (n + j * dp[i][j - 1]) / j;
      if (i != 0 && j == 0) dp[i][j] = (n + i * dp[i - 1][j]) / i;
      if (i != 0 && j != 0) {
        dp[i][j] = (n * n + i * j * dp[i - 1][j - 1] +
                    i * (n - j) * dp[i - 1][j] + (n - i) * j * dp[i][j - 1]) /
                   (n * (i + j) - i * j);
      }
    }
  }
  cout << fixed << setprecision(10);
  cout << dp[a][b];
  return 0;
}
