#include <bits/stdc++.h>
using namespace std;
void qmax(int &x, int y) {
  if (x < y) x = y;
}
void qmin(int &x, int y) {
  if (x > y) x = y;
}
inline int read() {
  char s;
  int k = 0, base = 1;
  while ((s = getchar()) != '-' && s != EOF && !(isdigit(s)))
    ;
  if (s == EOF) exit(0);
  if (s == '-') base = -1, s = getchar();
  while (isdigit(s)) k = k * 10 + (s ^ '0'), s = getchar();
  return k * base;
}
inline void write(long long x) {
  static char cnt, num[20];
  cnt = 0;
  if (!x) {
    putchar('0');
    return;
  }
  for (; x; x /= 10) num[++cnt] = x % 10;
  for (; cnt; putchar(num[cnt--] + 48))
    ;
}
const int maxn = 2010;
double f[maxn][maxn];
int n, m, cnt[maxn], cntx, cnty;
bool v1[maxn], v2[maxn];
int main() {
  n = read();
  m = read();
  if (m == 0) cntx = 1, cnty = 1;
  for (int i = 1, x, y; i <= m; i++) {
    x = read(), y = read();
    if (!v1[x]) v1[x] = 1, cntx++;
    if (!v2[y]) v2[y] = 1, cnty++;
  }
  for (int i = n; i >= cntx; i--) {
    for (int j = n; j >= cnty; j--) {
      if (i == n && j == n)
        ;
      else
        f[i][j] =
            (n * n + f[i][j] + i * (n - j) * f[i][j + 1] +
             (n - i) * j * f[i + 1][j] + (n - i) * (n - j) * f[i + 1][j + 1]) /
            ((double)n * n - i * j);
    }
  }
  if (m == 0) f[cntx][cnty] += 1;
  printf("%.10lf", f[cntx][cnty]);
  return 0;
}
