#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    count=0
    c=s
    while(c>6):
        count=count+1
        k=p-d
        if(c>=m and k>=6):
            c=c-p
            p=p-d
        else:
            c=c-6
    return count

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