#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
long long C[61][61];
void c() {
  C[0][0] = C[1][0] = C[1][1] = 1;
  for (long long i = 0; i < 61; i++) C[i][0] = 1;
  for (long long i = 2; i < 61; i++) {
    for (long long j = 1; j <= i; j++) {
      C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long n, m, t;
  cin >> n >> m >> t;
  long long ans = 0, nn = n, mm = m;
  c();
  while (nn >= 4 || ((t - nn) >= 1) && (t - nn) <= m) {
    if (n >= nn && m >= t - nn && nn >= 4 && t - nn >= 1)
      ans += (C[n][nn] * C[m][t - nn]);
    nn--;
  }
  cout << ans << endl;
  return 0;
}
