#include <bits/stdc++.h>
using namespace std;
int main() {
  int c = 0, v, a, b, k, m, n, z = 0, x = 0;
  cin >> v >> a >> b >> k;
  m = b / (v - 1);
  n = v * k;
  for (int i = 1; i <= m; i++) {
    z = z + n;
    x++;
    if (z >= a) {
      c++;
      break;
    }
  }
  if (c == 0) {
    m = m * (v - 1);
    b = b - m;
    b = (b + 1) * k;
    z = z + b;
    x++;
    if (z < a) {
      a = a - z;
      if (a % k == 0) {
        a = a / k;
        x = x + a;
      } else {
        a = a / k;
        x = x + a + 1;
      }
    }
  }
  cout << x;
  cin >> a;
}
