#include <bits/stdc++.h>
using namespace std;
const int MAX = (1 << 15) + 100;
const int inf = 522133279;
long long C(int n, int m) {
  long long fenzi = 1;
  int fenmu = 1;
  for (int i = n - m + 1; i <= n; i++) {
    fenzi *= i;
    fenzi /= fenmu++;
  }
  return fenzi;
}
int main() {
  int m, n, t;
  cin >> m >> n >> t;
  long long ans = 0;
  for (int i = 1; i <= t - 4; i++) {
    if (i <= n && t - i <= m) ans += C(m, t - i) * C(n, i);
  }
  cout << ans << endl;
  return 0;
}
