#include <bits/stdc++.h>
using namespace std;
long long int dp[100][100];
long long int ncr(long long int n, long long int r) {
  if (dp[n][r] != 0) return dp[n][r];
  if (n == r) return 1;
  if (r == 1)
    return n;
  else {
    dp[n][r] = ncr(n - 1, r) + ncr(n - 1, r - 1);
    return dp[n][r];
  }
}
int main() {
  long long int n, m, t, i, j, b, g, sum = 0;
  cin >> n >> m >> t;
  if (n == 4) {
    cout << ncr(m, t - 4) << endl;
    return 0;
  }
  if (t > n) {
    b = n;
    g = t - b;
  } else {
    b = t - 1;
    g = 1;
  }
  while (b >= 4 && g <= m) {
    sum += (ncr(n, b) * ncr(m, g));
    b--;
    g++;
  }
  cout << sum << endl;
}
