#include <bits/stdc++.h>
using namespace std;
unsigned long long Newton(unsigned long long n, unsigned long long k) {
  if (k == 0 || k == n)
    return 1;
  else {
    unsigned long long wyn = 1;
    if (k > n / 2) k = n - k;
    for (int j = 1; j <= k; ++j) wyn = wyn * (n - j + 1) / j;
    return wyn;
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  unsigned long long n, m, t;
  cin >> n >> m >> t;
  unsigned long long wyn = 0;
  for (int ch = 4; ch <= n; ++ch)
    if (t - ch <= m && t - ch > 0) wyn += Newton(n, ch) * Newton(m, t - ch);
  cout << wyn;
  return 0;
}
