#include <bits/stdc++.h>
using namespace std;
map<pair<int, int>, int> dp;
long long c(int x, int y) {
  if (x == 0 || x == y) return 1;
  pair<int, int> key = {x, y};
  if (dp.count(key) == 0) dp[key] = c(x - 1, y - 1) + c(x, y - 1);
  return dp[key];
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, m, t;
  cin >> n >> m >> t;
  long long ans = 0;
  int start = max(4, t - m);
  int limit = min(t - 1, n);
  for (int i = start; i <= limit; ++i) {
    int j = t - i;
    ans += c(i, n) * c(j, m);
  }
  cout << ans << "\n";
  return 0;
}
