#include <bits/stdc++.h>
using namespace std;
int r[2010], c[2010];
long double dp[2010][2010];
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  int ri, ci;
  memset(r, 0, sizeof(r));
  memset(c, 0, sizeof(c));
  for (int i = 0; i < m; i++) {
    scanf("%d%d", &ri, &ci);
    r[ri - 1]++;
    c[ci - 1]++;
  }
  dp[0][0] = 0.0;
  for (int i = 1; i <= n; i++)
    dp[0][i] = dp[i][0] = dp[0][i - 1] + (long double)n / i;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= n; j++) {
      dp[i][j] = (long double)i / n * (long double)j / n * dp[i - 1][j - 1] +
                 (long double)(n - i) / n * (long double)j / n * dp[i][j - 1] +
                 (long double)i / n * (long double)(n - j) / n * dp[i - 1][j] +
                 1;
      dp[i][j] /= 1 - (long double)(n - i) / n * (long double)(n - j) / n;
    }
  int c1 = 0, c2 = 0;
  for (int i = 0; i < n; i++)
    if (!r[i]) c1++;
  for (int i = 0; i < n; i++)
    if (!c[i]) c2++;
  cout << dp[c1][c2];
  return 0;
}
