#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 */ 
    long long int i,p,d,m,s,c=0,flag=0;
    cin>>p>>d>>m>>s;
    for(i=1;i>=1;i++)
    {
        if(s>=p)
        {
            c++;
            s=s-p;
            if(flag==0)
                p=p-d;
            if(p<=m)
            {
                p=m;
                flag=1;
                
            }
            
            
        }
       else
           break;
        
    }
    cout<<c;
    return 0;
}