Is the Shelf Sorted?

You are given the number of books n on a shelf and a sequence of n integers representing the heights of the books in the order they are arranged. Your task is to determine whether the books are arranged in non-decreasing order by height.

If the sequence of heights is sorted in non-decreasing order, print YES. Otherwise, print NO.

The comparison should follow the mathematical form of:

\(h_1 \leq h_2 \leq \dots \leq h_n\)

where \(h_i\) represents the height of the \(i\)-th book.

inputFormat

The first line contains an integer n (\(1 \le n \le 10^5\)), the number of books on the shelf. The second line contains \(n\) space-separated integers representing the height of each book (each height is an integer between 1 and 10^9).

outputFormat

Output a single line containing YES if the sequence is sorted in non-decreasing order, or NO otherwise.

## sample

5
120 150 150 180 200

YES

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