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) {
         if(p>s){
            return 0;
        }
        long total = 1;
        long sum = p;
        p-=d;
        if(p<m){
            p=m;
        }
        while(p>=m && sum+p<=s){
            sum+=p;
            p-=d;
            total++;
        }
        
        if(p<m){
            p=m;
        }
        while(sum+p<=s){
            sum+=p;
            total++;
        }
        return (int)total;
    }

    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();
    }
}