#include <bits/stdc++.h>
using namespace std;
const int N = 300 + 7;
const long double INF = 1e99;
int n, m, k;
long double comb[N][N], sol, memoi[N * N];
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  for (int n = 0; n < N; n++) {
    comb[n][0] = 1;
    for (int k = 1; k <= n; k++) {
      comb[n][k] = comb[n - 1][k - 1] + comb[n - 1][k];
    }
  }
  cin >> n >> m >> k;
  memoi[0] = 1;
  for (int i = 1; i <= n * n; i++) {
    memoi[i] = memoi[i - 1] * (k + 1 - i) / (m + 1 - i);
  }
  for (int a = 0; a <= n; a++) {
    for (int b = 0; b <= n; b++) {
      int cnt = n * (a + b) - a * b;
      long double cur = comb[n][a] * comb[n][b] * memoi[cnt];
      sol += cur;
      if (sol > INF) {
        cout << "1e99\n";
        return 0;
      }
    }
    cout << "\n";
  }
  cout << fixed << setprecision(9) << sol << "\n";
  return 0;
}
