#include <bits/stdc++.h>
using namespace std;
long long int fun(long long int a, long long int b) {
  long long int ans = 1;
  if (a < b) return 0;
  for (int i = 1; i <= b; i++) {
    ans *= (a - b + i) / i;
  }
  return ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  long long int n, m, t;
  cin >> n >> m >> t;
  vector<vector<long long int>> com(n + m + 1,
                                    vector<long long int>(n + m + 1, 0));
  for (int i = 0; i <= n + m; i++) com[i][0] = 1;
  for (int i = 1; i <= n + m; i++) com[0][i] = 0;
  for (int i = 1; i <= n + m; i++) {
    for (int j = 1; j <= i; j++) {
      com[i][j] = com[i - 1][j - 1] + com[i - 1][j];
    }
  }
  long long int ans = com[n + m][t] - com[n][t] - com[n][3] * com[m][t - 3] -
                      com[n][2] * com[m][t - 2] - com[n][1] * com[m][t - 1] -
                      com[m][t];
  cout << ans << endl;
  return 0;
}
