import java.util.*;
import java.io.*;

class PRINCESS {
    
        public static void main(String args[]) throws Exception {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            int p,d,m,s;
            String str[]=br.readLine().split(" ");
            p=Integer.parseInt(str[0]);
            d=Integer.parseInt(str[1]);
            m=Integer.parseInt(str[2]);
            s=Integer.parseInt(str[3]);
            int ans=0;
            int rem=s,cost=p;
            while(rem>0){
                if(cost>rem){
                    break;
                }
                if(cost<=m){
                    //System.out.println(rem);
                    ans=ans+(rem)/m;
                    break;
                }
                ans++;
                rem=rem-cost;
                //System.out.println("rer"+rem);
                cost=cost-d;
                //System.out.println("cs"+cost);
            }
            System.out.println(ans);
        }

    }