#include <bits/stdc++.h>
using namespace std;
long long C[100][100];
void binomialCoeff(long long n, long long k) {
  long long i, j;
  for (i = 0; i <= n; i++) {
    for (j = 0; j <= min(i, k); j++) {
      if (j == 0 || j == i)
        C[i][j] = 1;
      else
        C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
}
int main() {
  long long n, m, t;
  scanf("%lld", &n);
  scanf("%lld", &m);
  scanf("%lld", &t);
  long long ans = 0;
  binomialCoeff(90, 90);
  for (long long i = 4; i <= t - 1 && i <= n; i++) {
    if (t - i <= m) {
      ans += C[n][i] * C[m][t - i];
    }
  }
  printf("%lld\n", ans);
  return 0;
}
