#include <bits/stdc++.h>
const int inf = 1 << 30;
const long long INF = 1ll << 61;
using namespace std;
int n, m;
int xx[20000 + 55], yy[20000 + 55];
double dp[2000 + 55][2000 + 55];
int cntx = 0, cnty = 0;
void init() {
  memset(xx, 0, sizeof(xx));
  memset(yy, 0, sizeof(yy));
  memset(dp, 0.00, sizeof(dp));
}
bool input() {
  while (cin >> n >> m) {
    cntx = cnty = n;
    for (int i = 0; i < m; i++) {
      int x, y;
      scanf("%d %d", &x, &y);
      if (!xx[x]) cntx--;
      if (!yy[y]) cnty--;
      xx[x]++;
      yy[y]++;
    }
    return false;
  }
  return true;
}
void cal() {
  dp[0][0] = 0.00;
  for (int i = 1; i <= n; i++) {
    dp[i][0] = dp[i - 1][0] + n * 1.0 / i;
    dp[0][i] = dp[0][i - 1] + n * 1.0 / i;
  }
  for (int i = 1; i <= cntx; i++) {
    for (int j = 1; j <= cnty; j++) {
      dp[i][j] += n * n * 1.0;
      dp[i][j] += i * j * dp[i - 1][j - 1];
      dp[i][j] += (n - i) * j * dp[i][j - 1];
      dp[i][j] += i * (n - j) * dp[i - 1][j];
      dp[i][j] /= (n * n - (n - i) * (n - j));
    }
  }
  printf("%.10lf\n", dp[cntx][cnty]);
}
void output() {}
int main() {
  while (true) {
    init();
    if (input()) return 0;
    cal();
    output();
  }
  return 0;
}
