#include <bits/stdc++.h>
using namespace std;
unsigned long long binomial(short n, short k) {
  auto result = 1LLU;
  if (n - k < k) {
    k = n - k;
  }
  for (int i = 1; i <= k; i++) {
    result *= (n - i + 1);
    result /= i;
  }
  return result;
}
int main() {
  ios_base::sync_with_stdio(false);
  int n, m, t;
  cin >> n >> m >> t;
  auto result = 0LLU;
  int minboy = max(4, t - m);
  int maxboy = min(n, t - 1);
  auto bin1 = binomial(n, minboy), bin2 = binomial(m, t - minboy);
  for (auto i = minboy; i <= maxboy; i++) {
    result += bin1 * bin2;
    bin1 *= (n - i);
    bin1 /= (i + 1);
    bin2 *= (t - i);
    bin2 /= (m - t + i + 1);
  }
  cout << result << endl;
  return 0;
}
