#include <bits/stdc++.h>
using namespace std;
ofstream out("output.txt");
const long long OO = 0x3f3f3f3f;
long long gcd(long long a, long long b) {
  if (a < b) swap(a, b);
  while (b) swap(a, b), b %= a;
  return a;
}
long long nCr(int n, int r) {
  int start = max(r, n - r) + 1;
  r = min(r, n - r);
  vector<int> numerator, dominator;
  for (int i = start; i <= (int)(n); ++i) numerator.push_back(i);
  for (int i = 0; i < (int)(r); ++i) {
    dominator.push_back(i + 1);
    for (int j = 0; j < (int)(((int)numerator.size())); ++j) {
      int common = gcd(numerator[j], dominator[i]);
      dominator[i] /= common, numerator[j] /= common;
    }
  }
  long long factorial_n = 1, factorial_d = 1;
  for (int i = 0; i < (int)(((int)numerator.size())); ++i)
    factorial_n *= numerator[i];
  for (int i = 0; i < (int)(((int)dominator.size())); ++i)
    factorial_d *= dominator[i];
  return factorial_n / factorial_d;
}
int main() {
  int n, m, t;
  cin >> n >> m >> t;
  long long res = 0;
  for (int i = 4; i <= (int)(n); ++i) {
    if (t - i < 1) break;
    if (t - i > m) continue;
    res += nCr(n, i) * nCr(m, (t - i));
  }
  cout << res;
  getchar();
  getchar();
  return 0;
}
