#include <bits/stdc++.h>

using namespace std;

int main() {
    int p,d,m,i,n,sum=0,c,x,y,z;
   long long int s;
    cin >> p >> d >> m >> s;
   sum=sum+p;
   while(p>=m&&sum<=s)
   {
       p=p-d;
       sum=sum+p;
       c++;
       if((p-d)==m)
       {
           while(p>=m&&sum<=s)
         {
       p=p-d;
       sum=sum+p;
       c++;
               
          }
       
       }
   }
   
    cout<<c+1;
   
    return 0;
}