Contest: Task: Related: TaskA TaskC

Score : $200$ points

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.

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

Input is given from Standard Input in the following format:

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

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.