import sys

def isValid(s: str) -> bool:
    stack = []
    mapping = {')': '(', ']': '['}

    for char in s:
        if char in '([':
            stack.append(char)
        elif char in ')]':
            if not stack or mapping[char] != stack.pop():
                return False

    return not stack

s = sys.stdin.readline().strip()
result = isValid(s)
print(str(result).lower())