import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution 
{

    public static void main(String[] args) 
    {
        Scanner in = new Scanner(System.in);
        int p = in.nextInt();
        int d = in.nextInt();
        int m = in.nextInt();
        int s = in.nextInt();
        int count=0;
        while(s>=p)
        {
            s=s-p;
            //System.out.println(p);
            count++;
            if(p>=m)
            {
                p=p-d;
                if(p<=m)
                    p=m;
            }
        }
        System.out.println(count);
        in.close();
    }
}