#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 m,p,d,s;
    cin>>p>>d>>m>>s;
    int count=0;
    while(s>0){
        if(s>=p){
            count++;
            s-=p;
            if(p>m)
            p-=d;
            if(p<=m){
                p=m;
            }
        }
        else{
            break;
        }
    }
    cout<<count;
    return 0;
}