#include <bits/stdc++.h>
long long int fact[61][61];
int min(int x, int y) { return x < y ? x : y; }
void pre_cal() {
  int i, j, k;
  for (i = 1; i <= 60; i++) {
    fact[i][0] = 1;
    fact[i][i] = 1;
    for (j = 1; j < i; j++) {
      fact[i][j] = fact[i - 1][j] + fact[i - 1][j - 1];
    }
  }
}
int main() {
  pre_cal();
  int n, m, i, j, t, k;
  scanf("%d %d %d", &n, &m, &t);
  long long int ways = 0;
  for (i = 4; i <= n; i++) {
    for (j = 1; j <= m; j++) {
      if (i + j == t) {
        ways = ways + fact[n][i] * fact[m][j];
      }
    }
  }
  printf("%I64d\n", ways);
  return 0;
}
