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(s < p){
            return 0;
        }
        int ans = p;
        int sum = p;
        int count = 1;
        boolean flag = false;
        while(ans <= s){
            flag = true;
            if(sum-d >= m){
                ans += sum-d; 
                sum = sum-d;
            }else{
                ans += m;
                sum = m;
            }
            count++;
        }
        
        if(flag){
            count--;
        }
        
        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();
    }
}