#include <bits/stdc++.h>
using namespace std;
map<pair<long long int, long long int>, int> m;
long long int comb(long long int n, long long int r) {
  int k1, k2;
  if (m[make_pair(n, r)] != 0) return m[make_pair(n, r)];
  if (r > n) return 0;
  if (n == r) return 1;
  if (r == 0) return 1;
  if (r == 1) return n;
  k1 = comb(n - 1, r - 1);
  k2 = comb(n - 1, r);
  m[make_pair(n - 1, r - 1)] = k1;
  m[make_pair(n - 1, r)] = k2;
  return k1 + k2;
}
int main() {
  long long int n, m, t, k1 = 0, k2 = 0, k3 = 0, sum = 0, i = 0, x, y;
  cin >> n >> m >> t;
  if ((n + m) < t) cout << 0;
  if (n < 4 || m < 1) cout << 0;
  for (x = 4; x <= t - 1; x++) {
    if (m >= (t - x)) sum += (comb(n, x) * comb(m, t - x));
  }
  cout << sum;
}
