#include <bits/stdc++.h>
int N, M, K;
double C[305][305];
double P[305];
int main() {
  scanf("%d %d %d", &N, &M, &K);
  C[0][0] = 1;
  for (int i = 1; i <= N; i++) {
    C[i][0] = 1;
    for (int j = 1; j <= N; j++) {
      C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
  P[0] = 1;
  for (int i = 0; i < N * N; i++) {
    P[i + 1] = P[i] * (K - i) / (M - i);
  }
  double ans = 0;
  for (int r = 0; r <= N; r++) {
    for (int c = 0; c <= N; c++) {
      if ((ans += C[N][r] * C[N][c] * P[N * (r + c) - r * c]) > 1e99) {
        puts("1e99");
        return 0;
      }
    }
  }
  printf("%.10lf\n", ans);
}
