#include <bits/stdc++.h>
using namespace std;
long long n, m, t, c[70][70], a;
int main() {
  c[0][0] = 1;
  for (long long i = 0; i < 70; i++) c[i][0] = c[i][i] = 1;
  for (long long i = 1; i < 70; i++) {
    for (long long j = 1; j < i; j++) c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
  }
  cin >> n >> m >> t;
  for (long long i = 4; i < t; i++) a += c[n][i] * c[m][t - i];
  cout << a;
}
