#include <bits/stdc++.h>
using namespace std;
int gn() {
  int i, j;
  i = getchar();
  while (!(((i) >= '0') && ((i) <= '9'))) i = getchar();
  j = (i - '0');
  i = getchar();
  while ((((i) >= '0') && ((i) <= '9'))) {
    j *= 10;
    j += (i - '0');
    i = getchar();
  }
  return j;
}
unsigned long long int nCr(unsigned long long int n, unsigned long long int r) {
  if (n - r < r) r = n - r;
  unsigned long long int ans = 1;
  for (unsigned long long int i = 1; i <= r; ++i) {
    ans = (ans * (n - i + 1)) / i;
  }
  return ans;
}
int main() {
  unsigned long long int n, m, t, ans = 0;
  cin >> n >> m >> t;
  for (int b = 4; b <= t - 1; ++b) {
    ans += nCr(n, b) * nCr(m, t - b);
  }
  cout << ans;
  return 0;
}
