#include<bits/stdc++.h>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    //int cost;
    int y=1;
    for(int i=s;i>=0;)
    {
        if(i==s)
            i=i-p;
        else
        {
            int x=(p-y*d);
            if(x<=m)
                x=m;
            i=i-x;
            y++;
        }
    }
    cout<<y-1<<"\n";
    return 0;
}