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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int p,d,m,tot,count=0,i,flag=1;
    cin>>p>>d>>m>>tot;
    while(flag==1)
    {
        tot=tot-p;
        if(p>=m)
        {
         p=p-d;
            if(p<m)
            {
                p=m;
            }
        }
        //cout<<"tot :"<<tot<<" p: "<<p<<"\n";
        if(tot>=0)
        {
            count+=1; 
        }
        //cout<<"count : "<<count<<"\n";
        if(tot<0){
            flag=0;
        }
        
    };
    cout<<count; 
    return 0;
}