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# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;


public class Contest
{
	public static void Main()
	{
		int[] a = Array.ConvertAll(Console.ReadLine().Split(' '), new Converter<string,int>(zzz => int.Parse(zzz)));

		int[] b = Array.ConvertAll(Console.ReadLine().Split(' '), new Converter<string,int>(zzz => int.Parse(zzz)));
		int[] c = Array.ConvertAll(Console.ReadLine().Split(' '), new Converter<string,int>(zzz => int.Parse(zzz)));
		int[] d = Array.ConvertAll(Console.ReadLine().Split(' '), new Converter<string,int>(zzz => int.Parse(zzz)));
/*
		int n = a[0];
		int[][] e = new int[n][];
		for(int i=0; i<n; i++) e[i] = Array.ConvertAll(Console.ReadLine().Split(' '), new Converter<string,int>(zzz => int.Parse(zzz)));
*/


		string ans = 1.ToString();

		Console.WriteLine(ans);
	}
	
	private static int calc_main(int[] a,int[] b,int[] c,int[] d) {



		return 0;
	}




}