#include <bits/stdc++.h>
using namespace std;
unsigned long long C[64][64];
int main() {
  C[0][0] = 1;
  for (int i = 1; i < 64; i++) {
    C[i][0] = C[i][i] = 1;
    for (int j = 1; j < i; j++) C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
  }
  int n, m, t;
  while (cin >> n >> m >> t) {
    unsigned long long x = 0;
    for (int i = 4; i <= n; i++) {
      int j = t - i;
      if (1 <= j && j <= m) x += C[n][i] * C[m][j];
    }
    cout << x << endl;
  }
  return 0;
}
