#include <bits/stdc++.h>
using namespace std;
long long N, M, t, ans, first[(int)2000 + 3];
long long C(long long n, long long r) {
  long long ans = 1;
  bool marked[77];
  memset(marked, 0, sizeof marked);
  for (int i = 0; i < r; i++) {
    ans *= n--;
    for (int j = 1; j <= r; j++) {
      if (!marked[j] && ans % j == 0) ans /= j, marked[j] = 1;
    }
  }
  long long x = 1;
  for (int i = 1; i <= r; i++)
    if (!marked[i]) x *= i;
  ans /= x;
  return ans;
}
int main() {
  ios::sync_with_stdio(false);
  first[0] = 1;
  for (int i = 1; i <= 1000; i++) {
    first[i] = i * first[i - 1];
  }
  cin >> N >> M >> t;
  for (int i = 4; i <= N; i++) {
    int j = t - i;
    if (j <= 0) continue;
    long long temp = C(N, i);
    temp *= C(M, j);
    ans += temp;
  }
  cout << ans;
  return 0;
}
