#include <bits/stdc++.h>
using namespace std;
long long ans;
inline long long com(int n, int m) {
  long long res = 1;
  for (register int i = m - n + 1; i <= m; ++i) res = res * i / (i - m + n);
  return res;
}
int main() {
  int n, m, t;
  scanf("%d%d%d", &n, &m, &t);
  for (register int i = max(1, t - n); i <= min(t - 4, m); ++i)
    ans += com(i, m) * com(t - i, n);
  printf("%I64d\n", ans);
  return 0;
}
