#include <bits/stdc++.h>

using namespace std;



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