#include <bits/stdc++.h>
using namespace std;
long long N = 2005;
vector<long long> row = {-1, 1, 0, 0};
vector<long long> col = {0, 0, -1, 1};
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, m, t;
  cin >> n >> m >> t;
  vector<long long> boy, girl;
  boy.push_back(1);
  girl.push_back(1);
  for (long long i = 1; i <= t - 1; i++) {
    boy.push_back(boy[i - 1] * (n - i + 1) / i);
    if (i <= t - 4) girl.push_back(girl[i - 1] * (m - i + 1) / i);
  }
  long long ans = 0;
  for (long long i = 1; i <= t - 4; i++) {
    long long g = i, b = t - i;
    if (g > m || b > n || b < 4 || g < 1) continue;
    ans = ans + boy[b] * girl[g];
  }
  cout << ans << '\n';
}
