#include <bits/stdc++.h>
using namespace std;
long long n, m, t;
long long C[40][40];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  C[1][1] = 1LL;
  for (int i = 2; i < 40; i++) {
    for (int j = 1; j <= i; j++) {
      C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
  cin >> n >> m >> t;
  long long solve = 0LL;
  for (long long i = 4; i <= n; i++) {
    for (long long j = 1; j <= m; j++) {
      if (i + j == t) {
        solve += C[n + 1][i + 1] * C[m + 1][j + 1];
      }
    }
  }
  cout << solve << '\n';
  return 0;
}
