int howManyGames(int p, int d, int m, int s) {
    int result = 0;
    while( s >= p){
        s -= p;
        p = max(m, p-d);
        result++;
    }
    return result;
}

int howManyGames(int p, int d, int m, int s){
    if( s < p) return 0;
    return howManyGames( max(m, p-d), d, m, s - p) + 1;
}

int howManyGames(int p, int d, int m, int s) {
    int n = 1 + (p - m) / d;
    int total = (p + p - (n - 1) * d) * n / 2;
    if(total <= s) {
        return n + (s - total) / m;
    }
    else 
        return 0;
        // this return need to be computed properly
}

/*
 * Cuddle time
 * Phuong Chi
 * Miss you
 */

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;


public class Solve_problems
{
    static int solve(int p, int d, int m, int s)
    {
        int gameBought=0;
        while(s>=p)
        {
            s-=p;
            ++gameBought;
            p=Math.max(p-d,m);// Ensure the price doesn't go below the minimum cost 'm'
        }
        return gameBought;
    }
    public static void main(String[] args) 
    {
        Scanner sc=new Scanner(System.in);
        
        int p = sc.nextInt();
        int d = sc.nextInt();
        int m = sc.nextInt();
        int s = sc.nextInt();
        
        System.out.println(solve(p, d, m, s));
        
        sc.close();
    }     
}

function howManyGames(p: number, d: number, m: number, s: number): number {
    let r = 0
    while(s - p >= 0){
        r++
        s -= p 
        p = p - d <= m ? m : p - d 
    }
    return r
}

def howManyGames(p, d, m, s):
    counter = 0
    while s >= 0:
        s -= p
        if s < 0:
            break
            
        if p > m+d:
            p -= d
        else:
            p = m
            
        counter += 1
    return counter

    int games=0;
    while(s >= p)
    {
        s -= p;
        
        if(p - d >= m)
            p -= d;
        else
            p = m;
        
        games++;
    }
    return games;