题目描述
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.
Examples
Input
5
5 2 3 4 1
Output
YES
Input
5
2 4 3 5 1
Output
NO
Input
7
1 2 3 4 5 6 7
Output
YES
输入格式
见题面
输出格式
见题面
样例输入
5
2 4 3 5 1
样例输出
NO