def isBalanced(expression):
    stack = []
    for ind in range(len(expression)):
        elem = ''
        if expression[ind] in '([{':
            stack.append(expression[ind])
        elif len(stack) > 0:
            elem = stack.pop()
        else:
            return 'NO'
        
        if (expression[ind] in ')' and elem != '(') \
            or (expression[ind] in '}' and elem != '{') \
            or (expression[ind] in ']' and elem != '['):
            return 'NO'
    return 'YES' if len(stack) == 0 else 'NO'