#include<bits/stdc++.h>
using namespace std;

int main(){
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    
    int ans=0;
    while(s>=p){
        ans++;s-=p;
        if(p-d<m){
            p=m;
        }else{
            p=p-d;
        }
    }
    cout<<ans<<endl;
}