#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
long double fac[N], prob[N], ans;
long double C(int x, int y) { return fac[x] / fac[y] / fac[x - y]; }
int main() {
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);
  fac[0] = prob[0] = 1;
  for (int i = (int)(1); i <= (int)(N - 1); i++) {
    fac[i] = fac[i - 1] * i;
    prob[i] = prob[i - 1] * (k + 1 - i) / (m + 1 - i);
  }
  for (int i = (int)(0); i <= (int)(n); i++)
    for (int j = (int)(0); j <= (int)(n); j++)
      ans += C(n, i) * C(n, j) * prob[n * (i + j) - i * j];
  cout << setprecision(15);
  if (ans < 1e99)
    cout << ans << endl;
  else
    puts("1e99");
}
