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

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