while 1:
    read = input()
    if read[0] == '.':
        break
    s = ""
    a = 0
    result = True
    for j in read:
        if j == "(" or j == ")" or j == "[" or j == "]":
            s += j
    for j in s:
        if j == "(" or j == "[":
            a += 1
        elif j == ")" or j == "]":
            a -= 1
            if a < 0:
                result = False
                break
        if "(]" in s:
            result = False
            break
        elif "[)" in s:
            result = False
            break

    if result == False:
        print("no")
    else:
        print("yes")