#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/STACK:1000000000")
static long long m1[70][70];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  m1[0][0] = 1;
  for (int i = 1; i <= 30; ++i) {
    m1[i][0] = 1;
    for (int j = 1; j <= 30; ++j) m1[i][j] = m1[i - 1][j - 1] + m1[i - 1][j];
  }
  long long n, m, t, r = 0;
  cin >> n >> m >> t;
  for (int i = 4; i < t; ++i)
    if (t - i >= 0) r += m1[n][i] * m1[m][t - i];
  cout << r << endl;
  return 0;
}
