#include <bits/stdc++.h>
using namespace std;
long long dp[65][65];
int main() {
  int n, m, t, i, j;
  dp[0][0] = 1;
  for (i = 1; i <= 60; i++) {
    dp[i][0] = 1;
    dp[i][1] = i;
  }
  for (i = 2; i <= 60; i++) {
    for (j = 1; j <= 60; j++) dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
  }
  scanf("%d", &n);
  scanf("%d", &m);
  scanf("%d", &t);
  long long ans = 0;
  for (i = 4; i <= n; i++) {
    j = t - i;
    if (j <= m && j >= 1) {
      ans += (dp[n][i] * dp[m][j]);
    }
  }
  cout << ans << endl;
  return 0;
}
