#include <bits/stdc++.h>
using namespace std;
long long c(long long n, long long m) {
  long long x = 1;
  for (long long i = m - n + 1; i <= m; i++) {
    x = x * i / (i - m + n);
  }
  return x;
}
signed main() {
  long long n, m, t;
  cin >> n >> m >> t;
  long long sum = 0;
  for (long long i = max(1ll, t - n); i <= min(m, t - 4); i++) {
    sum += c(i, m) * c(t - i, n);
  }
  cout << sum << endl;
  return 0;
}
