#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int k, a, b, v, r;
  r = 0;
  cin >> k >> a >> b >> v;
  while (b + 1 >= k && a > 0) {
    a -= k * v;
    b -= k, b++;
    r++;
  }
  while (b + 1 < k && a > 0) a -= (b + 1) * v, b = 0, r++;
  cout << r;
  return 0;
}
