#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
long long c[61][61];
void cal() {
  c[1][0] = c[1][1] = 1;
  for (int i = 2; i <= 60; i++) {
    c[i][0] = 1;
    for (int j = 1; j <= i; j++) c[i][j] = c[i - 1][j] + c[i - 1][j - 1];
  }
}
int main() {
  cal();
  long long n, m, t;
  scanf("%I64d%I64d%I64d", &n, &m, &t);
  long long ans = 0;
  for (int i = 4; i <= n; i++) {
    if (i < t && t - i <= m) ans += c[n][i] * c[m][t - i];
  }
  printf("%I64d\n", ans);
  return 0;
}
