#include <bits/stdc++.h>
using namespace std;
const int inf = (int)1e9;
const int mod = (int)1e9 + 7;
const double pi = acos(-1.0);
const double eps = 1e-9;
double dp[2020][2020];
int n, m, a[2020][2020], calced[2020][2020];
double calc(int r, int c) {
  if (r == 0 && c == 0) return 0;
  double &res = dp[r][c];
  if (calced[r][c]) return res;
  res = 0;
  calced[r][c] = 1;
  int k = r * c;
  int kr = (n - c) * r;
  int kc = (n - r) * c;
  int kl = (n - c) * (n - r);
  double ans = n * n;
  if (r && c) ans += k * 1.0 * calc(r - 1, c - 1);
  if (r) ans += kr * calc(r - 1, c);
  if (c) ans += kc * 1.0 * calc(r, c - 1);
  return res = ans / (n * n - kl * 1.0);
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0, x, y; i < m; i++) {
    scanf("%d%d", &x, &y);
    x--;
    y--;
    a[x][y] = 1;
  }
  int r = 0, c = 0;
  for (int i = 0; i < n; i++) {
    bool ok = 0;
    for (int j = 0; j < n; j++) {
      if (a[i][j]) ok = 1;
    }
    if (!ok) r++;
    ok = 0;
    for (int j = 0; j < n; j++) {
      if (a[j][i]) ok = 1;
    }
    if (!ok) c++;
  }
  printf("%.9lf\n", calc(r, c));
  return 0;
}
