#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void upmax(T& a, T b) {
  if (a < b) a = b;
}
template <class T>
inline void upmin(T& a, T b) {
  if (a > b) a = b;
}
const int maxn = 307;
const int maxm = 100007;
const int mod = 1000000007;
const int inf = 0x7fffffff;
const double eps = 1e-7;
typedef int arr[maxn];
typedef int adj[maxm];
inline int fcmp(double a, double b) {
  if (fabs(a - b) <= eps) return 0;
  if (a < b - eps) return -1;
  return 1;
}
inline int add(int a, int b) { return ((long long)a + b) % mod; }
inline int mul(int a, int b) { return ((long long)a * b) % mod; }
inline int dec(int a, int b) { return add(a, mod - b % mod); }
inline int Pow(int a, int b) {
  int t = 1;
  while (b) {
    if (b & 1) t = mul(t, a);
    a = mul(a, a), b >>= 1;
  }
  return t;
}
template <typename Type>
inline Type RD() {
  char c = getchar();
  Type x = 0, flag = 1;
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    flag = -1;
  else
    x = c - '0';
  while (isdigit(c = getchar())) x = x * 10 + c - '0';
  return x * flag;
}
inline char rdch() {
  char c = getchar();
  while (!isalpha(c)) c = getchar();
  return c;
}
int n, m, k;
double C[maxn][maxn], f[maxm];
void input() {
  n = RD<int>(), m = RD<int>(), k = RD<int>();
  for (int i = 0, _ = n; i <= _; i++) {
    C[i][0] = 1;
    for (int j = 1, _ = i; j <= _; j++) C[i][j] = C[i - 1][j] + C[i - 1][j - 1];
  }
  f[0] = 1;
  for (int i = 1, _ = k; i <= _; i++)
    f[i] = f[i - 1] * (k - i + 1) / (m - i + 1);
}
void solve() {
  double ans = 0;
  for (int i = 0, _ = n; i <= _; i++) {
    for (int j = 0, _ = n; j <= _; j++) {
      ans += C[n][i] * C[n][j] * f[(i + j) * n - i * j];
      if (ans > 1e99) break;
    }
    if (ans > 1e99) break;
  }
  if (ans > 1e99) ans = 1e99;
  printf("%.10lf\n", ans);
}
int main() {
  input();
  solve();
  return 0;
}
