Valid Parentheses Checker

Given a string consisting solely of the characters '(', ')', '{', '}', '[' and ']', your task is to determine if the input string is a valid sequence of parentheses.

A sequence is considered valid if:

• Every opening bracket has a corresponding closing bracket of the same type.
• The brackets are closed in the correct order.

An empty string is also considered a valid sequence.

The validity condition can be mathematically expressed using a stack data structure. In particular, for any input string \( S \), the sequence is valid if and only if after processing all characters with the following rule, the stack is empty:

For each character \( c \) in \( S \):

• If \( c \) is an opening bracket, push it onto the stack.
• If \( c \) is a closing bracket, check if the top of the stack is the matching opening bracket. If it is, pop the top element; otherwise, the sequence is invalid.

inputFormat

The input consists of a single line containing a string of characters. The string will only include the characters '(', ')', '{', '}', '[' and ']'.

outputFormat

Output a single line: YES if the parentheses sequence is valid, and NO otherwise.

()

YES