#include <bits/stdc++.h>
using namespace std;
template <typename T>
void read(T &x) {
  x = 0;
  char ch = getchar();
  int fh = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') fh = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  x *= fh;
}
template <typename T>
void write(T x) {
  if (x < 0) x = -x, putchar('-');
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
template <typename T>
void writeln(T x) {
  write(x);
  puts("");
}
int n, m;
set<int> st1, st2;
double dp[2005][2005];
signed main() {
  read(n);
  read(m);
  for (int i = 1; i <= n; ++i) {
    st1.insert(i);
    st2.insert(i);
  }
  while (m--) {
    int r, c;
    read(r);
    read(c);
    st1.erase(r);
    st2.erase(c);
  }
  for (int i = 0; i <= st1.size(); ++i)
    for (int j = 0; j <= st2.size(); ++j) {
      if (i == 0 && j == 0) {
        dp[i][j] = 0;
      } else if (i == 0) {
        double tmp = (dp[i][j - 1] + 1) * (double)j / (double)n +
                     (double)(n - j) / (double)n;
        dp[i][j] = tmp / ((double)j / (double)n);
      } else if (j == 0) {
        double tmp = (dp[i - 1][j] + 1) * (double)i / (double)n +
                     (double)(n - i) / (double)n;
        dp[i][j] = tmp / ((double)i / (double)n);
      } else {
        double tmp =
            (dp[i][j - 1] + 1) * (double)j * (n - i) / (double)(n * n) +
            (dp[i - 1][j] + 1) * (double)i * (n - j) / (double)(n * n) +
            (dp[i - 1][j - 1] + 1) * (double)i * j / (double)(n * n) +
            (double)(n - i) * (n - j) / (double)(n * n);
        dp[i][j] =
            tmp / (double)(1 - (double)(n - i) * (n - j) / (double)(n * n));
      }
    }
  cout << fixed << setprecision(12) << dp[st1.size()][st2.size()] << endl;
  return 0;
}
