#include <bits/stdc++.h>
const double eps = 1e-9;
const double pi = acos(-1);
using namespace std;
long long C(int n, int k) {
  long long result[100];
  for (int i = 1; i <= n; i++) {
    result[i] = 1;
    for (int j = i - 1; j >= 1; j--) {
      result[j] = result[j - 1] + result[j];
    }
    result[0] = 1;
  }
  return result[k];
}
int main() {
  int n, m, t;
  while (cin >> n >> m >> t) {
    int free = t - 5;
    int a = n - 4, b = m - 1;
    long long ans = 0;
    for (int i = 4; i < t; i++) {
      if (i > n || t - i > m) continue;
      ans += C(n, i) * C(m, t - i);
    }
    cout << ans << endl;
  }
  return 0;
}
