#include <bits/stdc++.h>

using namespace std;



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