#include <bits/stdc++.h>
using namespace std;
int n, m, t;
long long ans, c[100][100];
long long f(int r, int n) {
  if (c[r][n] != -1) return c[r][n];
  if (r > n) return c[r][n] = 0;
  if (r == 0 || r == n) return c[r][n] = 1ll;
  return c[r][n] = f(r - 1, n - 1) + f(r, n - 1);
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  for (int i = 0; i < 31; i++)
    for (int j = 0; j < 31; j++) c[i][j] = -1;
  cin >> n >> m >> t;
  for (int i = 4; i <= min(t - 1, n); i++) ans += f(i, n) * f(t - i, m);
  cout << ans << endl;
}
