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

public class Solution {

    static int howManyGames(int p, int d, int m, int s) {
        int k=0,a=0;
   kush:for(int i=p;i>=m;)
         {
             if(i>m)
             {
             k=s-i;
                 
                  if(k>0)
                 a++;
                 
                 i-=d;
             
              
          
                 
             
             }
       else if(i<m)
           i=m;
       else if(i==m)
       {
           k=s-m;
           if(k>=0)
           {
               a++;
           }
           else if(k<0)
               i=0;
           
       }
         }
        return a+1;
    }

    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 answer = howManyGames(p, d, m, s);
        System.out.println(answer);
        in.close();
    }
}