#include <bits/stdc++.h>
using namespace std;
long long int cm(int n, int k) {
  if (k > n) {
    return 0;
  }
  long long int r = 1;
  for (int d = 1; d <= k; ++d) {
    r *= n--;
    r /= d;
  }
  return r;
}
int main() {
  int n, m, t;
  cin >> n >> m >> t;
  int b, g;
  long long int count = 0;
  for (b = 4; b <= t - 1; b++) {
    for (g = 1; g <= t - 4; g++) {
      if (b + g == t) {
        count += cm(n, b) * cm(m, g);
      }
    }
  }
  cout << count << endl;
  return 0;
}
