#!/bin/python

import sys

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

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