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 sum=0,count=0;
       
           
            
               while(p>m)
                {
                    sum=sum+p;
                    p=p-d;
                    count++;
                   
                }
            
                while(s-sum>=m)
                {
                    sum=sum+p;
                    count++;
                   
                }
            
        System.out.println(count);
    }
}