#include <bits/stdc++.h>
using namespace std;
int n, m;
int nr[2010], nc[2010];
double dp[2010][2010];
int main() {
  scanf("%d%d", &n, &m);
  int tr = 0, tc = 0;
  for (int i = 1; i <= m; i++) {
    int r, c;
    scanf("%d%d", &r, &c);
    if (!nr[r]) {
      tr++;
      nr[r]++;
    }
    if (!nc[c]) {
      tc++;
      nc[c]++;
    }
  }
  dp[n][n] = 0;
  for (int i = n; i >= 0; i--) {
    for (int j = n; j >= 0; j--) {
      if (i != n || j != n)
        dp[i][j] =
            (double)((n - i) * j * dp[i + 1][j] + i * (n - j) * dp[i][j + 1] +
                     (n - i) * (n - j) * dp[i + 1][j + 1] + n * n) /
            (n * n - i * j);
    }
  }
  printf("%.10lf\n", dp[tr][tc]);
  return 0;
}
