#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  for (int i = 0; i < 1000; i++) {
    d -= c;
    b -= c;
    if (a == 0 || b < 0 || d <= 0) {
      cout << i << endl;
      return 0;
    }
    a--;
    d--;
  }
  return 0;
}