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 scan = new Scanner(System.in);
		int p = scan.nextInt(),d = scan.nextInt(),m = scan.nextInt(),s = scan.nextInt();
		int number = 0;
		int currentCost = p;
		while(s > currentCost){
			s-=currentCost;
			number++;
			if(currentCost-d > m)
				currentCost-=d;
			else{
				number+=s/m;
				break;
			}
		}
		System.out.println(number);
    }
}