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=p,l=0;
        int z=p;
        while(count<=s){
             //System.out.println(z +"-" + count);
            z=z-d;
            if(z<=m){
                z=m;
                count=count+z;
                l++;
            }
            else{
        count=count+z;
            l++;
            }
        }
        return l;
    }

    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();
    }
}