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

int main(void){
    int p,d,m,s;
    scanf("%d %d %d %d",&p,&d,&m,&s);
    int ans=0;
    while(true){
        if(s>=p)ans++,s-=p;
        else break;
        if(p>m)
            p-=d;
        if(p<=m)p=m;
    }
    printf("%d\n",ans);
    return 0;
}