#include <bits/stdc++.h>
using namespace std;
const int N = 2005;
int n, m, r, c, row[N], col[N];
double dp[N][N];
int main() {
  scanf("%d%d", &n, &m);
  r = c = n;
  for (int i = 1; i <= m; ++i) {
    int u, v;
    scanf("%d%d", &u, &v);
    if (!row[u]) row[u] = 1, r--;
    if (!col[v]) col[v] = 1, c--;
  }
  dp[0][0] = 0;
  for (int i = 1; i <= n; ++i) {
    dp[i][0] = dp[i - 1][0] + 1.0 * n / i;
    dp[0][i] = dp[0][i - 1] + 1.0 * n / i;
  }
  for (int i = 1; i <= r; ++i) {
    for (int j = 1; j <= c; ++j) {
      dp[i][j] = n * n + i * j * dp[i - 1][j - 1] + (n - i) * j * dp[i][j - 1] +
                 i * (n - j) * dp[i - 1][j];
      dp[i][j] /= (double)(1.0 * n * n - (n - i) * (n - j));
    }
  }
  printf("%.10lf\n", dp[r][c]);
  return 0;
}
