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) {
		// Return the number of games you can buy
		if (p > s) {
			return 0;
		}
		int k=p;
		int i = 0;

		while (s-k >= 0) {
            s-=k;
			++i;
			k = k-d<=m?m:k-d;
            
		}
		return i;
	}


    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();
    }
}