#include<bits/stdc++.h>
using namespace std;
int main()
{   
    ios_base::sync_with_stdio(false);
    long long d,m,p,s,count;
    cin>>p>>d>>m>>s;
    count=0;
    while(s>=p)
    {
        count++;
        s-=p;
       p=max(m,p-d);
    }
    cout<<count;
}