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 i;
        int sum=0;
        int count=0;
        for(i=p;i>m;i-=d){
            sum+=i;
            count++;
        }
        //System.out.println(count);
        for(;sum<=s;){
            count++;
            sum+=i;
        }
        count-=2;
        //System.out.println(sum);
        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();
    }
}