import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int p = sc.nextInt(), d = sc.nextInt(), m = sc.nextInt(), s = sc.nextInt();
        int count = 0;
        while (s >=0){
        	if ((p -(count*d)) < m ){
        		s = s - m;
        	} else{
        		s = s - (p -(count*d));
        	}
//        	System.out.print(s+" ");
        	count++;
        }
//        System.out.println();
        System.out.println(count-1);
        sc.close();
    }
}