#include <bits/stdc++.h>
using namespace std;
long long combi(int m, int k) {
  if (k > m) return 0;
  int x = min(k, m - k);
  long long ans = 1;
  for (int i = 1; i <= x; i++) ans = 1LL * ans * (m - i + 1) / i;
  return ans;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, m, t;
  cin >> n >> m >> t;
  long long ans = combi(m + n, t) - combi(n, t) -
                  n * (n - 1) * (n - 2) / 6 * combi(m, t - 3) -
                  n * (n - 1) / 2 * combi(m, t - 2) - n * combi(m, t - 1) -
                  combi(m, t);
  cout << ans << endl;
}
