#include <bits/stdc++.h>
using namespace std;
int k, a, b, v;
int ans;
bool check(int x) { return a <= (x + min(b, x * (k - 1))) * v; }
void input() { cin >> k >> a >> b >> v; }
void output() {
  for (int i = 1;; i++)
    if (check(i) == true) {
      ans = i;
      break;
    }
  cout << ans << endl;
}
int main() {
  input();
  output();
}
