#include <bits/stdc++.h>
using namespace std;
long long N, M, T;
long long ans = 0;
long long C(long long n, long long m) {
  long long res = 1;
  for (long long i = m - n + 1; i <= m; ++i) {
    res = res * i / (i - m + n);
  }
  return res;
}
signed main() {
  cin >> N >> M >> T;
  for (long long i = max(1ll, T - N); i <= min(M, T - 4ll); ++i) {
    ans += C(i, M) * C(T - i, N);
  }
  cout << ans << endl;
  return 0;
}
