//
// Created by ubuntu on 9/9/17.
//

#include <iostream>

using namespace std;

int main (){
    int p,d,m,s;
    cin >> p >> d >> m >> s;

    int ans=0;
    s-=p;
    while(s>=0){
        p=(p-d>m)?p-d:m;
        s-=p;
        ans++;
    }
    cout << ans;
    return 0;
}