#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  if (a < b) swap(a, b);
  if (b == 0)
    return a;
  else
    gcd(b, a % b);
}
int main() {
  long long int ncr[62][62];
  for (long long int i = 0; i < 62; i++) {
    ncr[i][0] = 1;
    ncr[i][i] = 1;
  }
  for (long long int i = 1; i < 62; i++) {
    for (long long int j = 1; j <= i; j++) {
      ncr[i][j] = ncr[i - 1][j - 1] + ncr[i - 1][j];
    }
  }
  long long int n, m, t, ans = 0;
  cin >> n >> m >> t;
  for (long long int i = 4; i <= t - 1; i++) {
    ans += (ncr[n][i] * ncr[m][t - i]);
  }
  cout << ans << endl;
}
