#include <bits/stdc++.h>
using namespace std;
long long C(int n, int m) {
  long long z = 1;
  for (int i = 0; i < m; ++i) z = z * (n - i) / (i + 1);
  return z;
}
int main() {
  long long n, m, p;
  cin >> n >> m >> p;
  cout << C(n + m, p) - C(n, p) - C(m, p) - C(n, 1) * C(m, p - 1) -
              C(n, 2) * C(m, p - 2) - C(n, 3) * C(m, p - 3);
  return 0;
}
