#include <bits/stdc++.h>
using namespace std;
int n, m, t;
long long ans, c[62][62];
int main() {
  for (int i = 0; i < 62; ++i) {
    c[i][0] = 1;
    for (int j = 1; j <= i; ++j) {
      c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
    }
  }
  cin >> n >> m >> t;
  for (int guys = 4; guys <= t - 1; ++guys) {
    ans += c[n][guys] * c[m][t - guys];
  }
  cout << ans << endl;
  return 0;
}
