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: Runtime Error)

import java.util.*;

public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		int num = scan.nextInt();
		int[] ar = new int[num];
		for(int i = 0;i<num;i++){
			ar[i] = scan.nextInt();
		}
		int[] e = new int[1];
		int[] log = new int[1];
		int k = 0;
		for(int j = 0;j<num-1;j++){
			if(ar[j+1]<ar[j]&&k!=1){
				e[0]=ar[j];
				log[0]=j;
				k++;
			}else if(ar[j+1]<ar[j]&&k==1){
				e[1]=ar[j];
				log[1]=j;
				break;
			}
		}
		ar[log[0]]=e[1];
		ar[log[1]]=e[0];
		for(int l = 0;k<num-1;k++){
			if(ar[l+1]<ar[l]){
				System.out.println("NO");
			}else{
				System.out.println("YES");
			}
		}
	}
}