#include <bits/stdc++.h>

using namespace std;


int main() {
    int p;
    int d;
    int m;
    int s;
    long long int ans=0,spent=0;
    cin >> p >> d >> m >> s;
    while(s>=0)
    {   
     if(spent==0)
     {
      s=s-p;
      spent=spent+p;
      ans++;   
     }
     else
     {
      if((p-d)<=m)
      {
       p=m;
       d=0; 
      }
      else
      {
       p=p-d;   
      }
      s=s-p;
      spent=spent+p;
      ans++;   
     }    
    }
    ans--;
    cout<<ans;
    return 0;
}