#include <bits/stdc++.h>
using namespace std;
const int MAXN = 60;
long long nCr[MAXN + 1][MAXN + 1];
void fast_io() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
void prepare() {
  for (int i = 0; i <= MAXN; i++) {
    nCr[i][0] = 1;
  }
  for (int i = 1; i <= MAXN; i++) {
    for (int j = 1; j <= MAXN; j++)
      nCr[i][j] = nCr[i - 1][j] + nCr[i - 1][j - 1];
  }
}
int main() {
  fast_io();
  prepare();
  int n, m, t;
  cin >> n >> m >> t;
  long long ans = 0;
  for (int i = 4; i <= t - 1; i++) {
    ans += (nCr[n][i] * nCr[m][t - i]);
  }
  cout << ans << '\n';
  return 0;
}
