#include <bits/stdc++.h>
using namespace std;
using namespace std;
int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
int main() {
  int d[3], k;
  cin >> d[0] >> d[1] >> d[2] >> k;
  k = min(k, d[0] + d[1] + d[2] - 3);
  unsigned long long p[3] = {1, 1, 1};
  unsigned long long rv = 1;
  for (int i = 0; i != k; ++i) {
    int bj = -1;
    unsigned long long q = p[0] * p[1] * p[2];
    unsigned long long a = 0;
    for (int j = 0; j != 3; ++j) {
      if (p[j] < d[j]) {
        unsigned long long aa = q / p[j];
        if (aa > a) {
          a = aa;
          bj = j;
        }
      }
    }
    ++p[bj];
    rv += a;
  }
  cout << rv << endl;
  return 0;
}
