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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	static int nums[] , copys[] ;
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner (System.in) ;
		
		int N = in.nextInt() ;
		
		nums = new int [N] ;
		
		copys = new int [N] ;
		
		for(int i=0;i<N;i++) {
			
			nums[i] = in.nextInt() ;
			
			copys[i] = nums[i] ;
		
		}
		
		Arrays.sort(copys);
		
		int cnt = 0 ;
		
		for(int i=0;i<N;i++) {
			if(copys[i]!=nums[i])
				cnt++ ;
		}
		
		if(cnt>2) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
		
		in.close() ;
	}

}