#include <bits/stdc++.h>
using namespace std;
unsigned long long data[31] = {0};
unsigned long long Cmn(unsigned long long m, unsigned long long n) {
  unsigned long long tmp = 1;
  if (n >= m / 2) n = m - n;
  if (m == 30 && n == 15) return 155117520;
  for (unsigned long long i = m; i >= (m - n + 1); i--) {
    tmp *= i;
  }
  tmp /= data[n];
  return tmp;
}
int main() {
  data[0] = 1;
  for (unsigned long long i = 1; i <= 15; i++) {
    data[i] = data[i - 1] * (unsigned)i;
  }
  unsigned long long n = 0;
  unsigned long long m = 0;
  unsigned long long t = 0;
  cin >> n >> m >> t;
  unsigned long long count = 0;
  for (unsigned long long i = 4; i <= t - 1; i++) {
    if ((t - i) > m) continue;
    if (i > n) break;
    count += (Cmn(n, i) * Cmn(m, t - i));
  }
  cout << count << endl;
  return 0;
}
