#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long int n, m, t;
  cin >> n >> m >> t;
  long long int pascal[n + m + 2][n + m + 2];
  memset(pascal, 0, sizeof(pascal));
  pascal[0][0] = 1;
  for (long long int i = 1; i <= m + n; i++) {
    pascal[i][0] = pascal[i][i] = 1;
    for (long long int j = 1; j < i; j++) {
      pascal[i][j] = pascal[i - 1][j - 1] + pascal[i - 1][j];
    }
  }
  long long int ans =
      pascal[n + m][t] -
      (pascal[n][0] * pascal[m][t] + (pascal[n][1] * pascal[m][t - 1]) +
       (pascal[n][2] * pascal[m][t - 2]) +
       (pascal[n][3] * pascal[m][t - 3] + (pascal[n][t] * pascal[m][0])));
  cout << ans << endl;
}
