#include<bits/stdc++.h>
using namespace std;
int main()
{
    int p,d,m,s,i,j;
  scanf("%d %d %d %d",&p,&d,&m,&s);
  int c=0;

  while(s>=0)
  {
     s=s-p;
     if(s<0)
        break;
     else
        c++;
     if((p-d)>m)
        p-=d;
     else
        p=m;
  }
  printf("%d",c);


return 0;
}