#include<iostream>
using namespace std;
int main()
{
   int a,b,c,d;
   cin>>a>>b>>c>>d;
   int sum=0;
   int count=0;
   int k=a;
   while(sum<=d)
   {
     
     sum=sum+k;
     if(sum<=d)
     count++;
     if(k>c) k=k-b;

   }
   cout<<--count;
  return 0;
}