#include <bits/stdc++.h>
using namespace std;
long long comb[65][65];
int main() {
  int N, M, T;
  cin >> N >> M >> T;
  for (int i = 0; i <= 60; i++) {
    comb[i][0] = 1;
    for (int j = 1; j <= i; j++)
      comb[i][j] = comb[i - 1][j - 1] + comb[i - 1][j];
  }
  long long ans = comb[N + M][T] - comb[N][T];
  for (int i = 0; i < 4; i++) ans -= comb[N][i] * comb[M][T - i];
  cout << ans << endl;
  return 0;
}
