Problem:
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.

Sample Input 1

5
5 2 3 4 1

Sample Output 1

YES

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

Sample Input 2

5
2 4 3 5 1

Sample Output 2

NO

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

Sample Input 3

7
1 2 3 4 5 6 7

Sample Output 3

YES

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

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
int main()
{
	int N = 0, list[100] = { 0 }, A[100] = { 0 }, b = 0, C = 0, D = 0, E = 0, F = 0;
	cin >> N;
	for (int i = 0; i < N; i++)
	{
		cin >> list[i];
	}
	for (int i = 0; i < N; i++)
	{
		if (list[i] != i+1)
		{
			if (b == 0)
			{
				C = i;
			}
			if (b == 1)
			{
				D = i;
			}
			b += 1;
		}	
	}
	E = list[C];
	list[C] = list[D];
	list[D] = E;
	for (int i = 0; i < N; i++)
	{
		if (list[i] != i+1)
		{
			F = 1;
			break;
		}
	}
	if (F == 0)
	{
		cout << "Yes";
	}
	else
	{
		cout << "No";
	}
	return 0;}