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
        int count = 0;
		int rem =s;
		if (s<p){
			return 0;
		}
		if(s==p)
			return 1;
		
		while(rem>=m){
			if(count==0){
				rem -= p;
				count++;
				continue;
			}
			int k = p - (count*d);
			if (k<=m){
				k = m;
			}
			rem -= k;
			count++;
			if(rem<0)
				return count-1;
		}
		
		return count;
    }

    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();
    }
}