#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


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