#include <bits/stdc++.h>

using namespace std;



int main() 
{
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int c=0;
    while(1)
    {
        if(s<p)
            break;
        s=s-p;
        p=p-d;
        if(p<m)
            p=m;
        c++;
    }
    cout<<c<<endl;
    return 0;
}