Zigzag Number Checker

You are given a positive integer. Your task is to determine whether the number is a Zigzag Number.

A number is considered a Zigzag Number if for every three consecutive digits \(x, y, z\), the following condition holds:

• Either \(x z\) or \(x > y < z\)

If the number has fewer than three digits, it is not considered a Zigzag Number.

For example, given the number 121, the digits form a zigzag pattern because \(1 1\), so the output should be YES. Conversely, for the number 123, the pattern is not zigzag (\(1 < 2 < 3\)), so the output should be NO.

Read the input from standard input and output the result to standard output.

inputFormat

The input consists of a single line containing a positive integer \(n\).

Example:

121

outputFormat

Output a single line containing either YES if \(n\) is a Zigzag Number, or NO otherwise.

## sample

1

NO