while True:
    stack = []
    line = input()
    if line=="." :
        break

    isBalance = True
    for c in line:
        if c == "(":
            stack.append(c)
        elif c== ")":
            if not stack or stack[-1] != "(":
                isBalance = False
                break
            stack.pop()
        elif c == "[":
            stack.append(c)
        elif c== "]":
            if not stack or stack[-1] != "[":
                isBalance = False
                break
            stack.pop()
    print("yes" if isBalance and not stack else "no")