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 sum=0;
        sum+=p;
        int ans=1;
		while(s-sum>0){
            p-=d;
            if(p<m)
                break;
			sum+=p;
            ans++;
		}
        int rem=s-sum;
        //System.out.println(rem);
		return ans+(rem/m);
    }

    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();
    }
}