#include <bits/stdc++.h>
using namespace std;
long long int choose[40][40];
void choosePrecompute(int limit) {
  choose[0][0] = 1;
  for (int n = 1; n <= limit; n++) {
    choose[n][0] = 1;
    for (int k = 1; k <= n; k++) {
      choose[n][k] = (choose[n - 1][k] + choose[n - 1][k - 1]);
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  choosePrecompute(35);
  int n, m, t;
  cin >> n >> m >> t;
  long long int ans = 0;
  for (int girls = 1; girls <= m; girls++) {
    int boys = t - girls;
    if (boys < 4 or boys > n) continue;
    ans += choose[n][boys] * choose[m][girls];
  }
  cout << ans << endl;
  return 0;
}
