#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    ans = 0
    price = p 
    
    while s- price >= 0:
        #print s, price, ans 
        s -= price
        if price - d >= m :
            price -= d 
             
        else:
            price = m 
        ans += 1
    return ans 
            
        

if __name__ == "__main__":
    p, d, m, s = raw_input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print answer