#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:1000000000")
using namespace std;
const int maxn = (int)2e3 + 10;
bool x[maxn], y[maxn];
int n;
double dp[maxn][maxn];
bool used[maxn][maxn];
double go(int a, int b) {
  if (used[a][b]) {
    return dp[a][b];
  }
  if (a == 0 && b == 0) {
    dp[a][b] = 0;
    return 0;
  }
  used[a][b] = true;
  double ver = 1 - 1.0 / n / n * (n - a) * (n - b);
  dp[a][b] = 1 / ver;
  if (a != 0 && b != 0) dp[a][b] += (go(a - 1, b - 1)) / n / n * a * b / ver;
  if (a != 0) dp[a][b] += (go(a - 1, b)) / n / n * a * (n - b) / ver;
  if (b != 0) dp[a][b] += (go(a, b - 1)) / n / n * (n - a) * b / ver;
  return dp[a][b];
}
int main() {
  cin >> n;
  int m;
  cin >> m;
  for (int i = 0; i < m; i++) {
    int a, b;
    scanf("%d %d", &a, &b);
    x[a] = true;
    y[b] = true;
  }
  int a = 0, b = 0;
  for (int i = 1; i <= n; i++) {
    if (!x[i]) {
      a++;
    }
    if (!y[i]) {
      b++;
    }
  }
  printf("%.10lf\n", go(a, b));
  return 0;
}
