#!/bin/python

import sys

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

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