#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int n;
    int sum=0,d,e,j;
    cin>>e>>d>>j>>n;
    int c=0;
    while(sum<=n)
    { sum+=e;if(e>=j)
    {   if(e-d>=j)
          e=e-d;
         else
           e=j;}
        
        c++;
    }
    cout<<c-1<<endl;
      
        
    
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}