#include <bits/stdc++.h>
using namespace std;
vector<vector<int> > AdjList;
long long int c[65][65];
void ini() {
  c[0][0] = c[1][0] = c[1][1] = 1;
  for (int i = 2; i < 65; i++) {
    c[i][0] = 1;
    int j;
    for (j = 1; j < i; j++) {
      c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
    }
    c[i][j] = 1;
  }
}
int main() {
  ini();
  long long int out = 0;
  int n, m, k;
  cin >> n >> m >> k;
  for (int i = 0; i <= k; i++) {
    int boy = i;
    int girl = k - i;
    if (boy <= n && girl <= m && boy >= 4 && girl >= 1) {
      out += c[n][boy] * c[m][girl];
    }
  }
  cout << out << endl;
  return 0;
}
