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B - 0 or 1 Swap

Score : $200$ points

Problem Statement

We have a sequence $p$ = {$p_1,\ p_2,\ ...,\ p_N$} which is a permutation of {$1,\ 2,\ ...,\ N$}.

You can perform the following operation at most once: choose integers $i$ and $j$ $(1 \leq i < j \leq N)$, and swap $p_i$ and $p_j$. Note that you can also choose not to perform it.

Print YES if you can sort $p$ in ascending order in this way, and NO otherwise.

Constraints

• All values in input are integers.
• $2 \leq N \leq 50$
• $p$ is a permutation of {$1,\ 2,\ ...,\ N$}.

Input

Input is given from Standard Input in the following format:

$N$

$p_1$ $p_2$ $...$ $p_N$

Output

Print YES if you can sort $p$ in ascending order in the way stated in the problem statement, and NO otherwise.

5
5 2 3 4 1

YES

You can sort $p$ in ascending order by swapping $p_1$ and $p_5$.

5
2 4 3 5 1

NO

In this case, swapping any two elements does not sort $p$ in ascending order.

7
1 2 3 4 5 6 7

YES

$p$ is already sorted in ascending order, so no operation is needed.