#include <bits/stdc++.h>
using namespace std;
long long int power(long long int a, long long int b) {
  long long int res = 1;
  a %= 1000000007;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % 1000000007;
    a = a * a % 1000000007;
  }
  return res;
}
long long int modInverse(long long int a) { return power(a, 1000000007 - 2); }
const int N = 500023;
bool vis[N];
vector<int> adj[N];
void solve() {
  long long int n, m;
  cin >> n >> m;
  set<long long int> row, col;
  for (int i = 1; i <= n; i++) {
    row.insert(i);
    col.insert(i);
  }
  for (long long int i = 0; i < m; i++) {
    long long int a, b;
    cin >> a >> b;
    if (row.find(a) != row.end()) row.erase(a);
    if (col.find(b) != col.end()) col.erase(b);
  }
  long long int r = row.size();
  long long int c = col.size();
  double dp[n + 1][n + 1];
  dp[0][0] = 0;
  for (int i = 1; i <= n; i++) {
    dp[i][0] = (double)n / i + dp[i - 1][0];
    dp[0][i] = (double)n / i + dp[0][i - 1];
  }
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      dp[i][j] = (n * n * 1.00 +
                  (i * j * dp[i - 1][j - 1] + (n - i) * j * dp[i][j - 1] +
                   i * (n - j) * dp[i - 1][j])) /
                 (n * (i + j) - i * j + 0.00);
    }
  }
  cout << fixed << setprecision(15);
  cout << dp[r][c] << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int T = 1;
  int t = 0;
  while (t++ < T) {
    solve();
  }
  cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC
       << "ms\n";
}
