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.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		 Scanner scan = new Scanner(System.in);
	     int r  = scan.nextInt();
	     ArrayList<Integer> list = new ArrayList<Integer>();
	     for(int i=0;i<r;i++) {
	    	 list.add(scan.nextInt());
	     }

	     @SuppressWarnings("unchecked")
		ArrayList<Integer> sorted =(ArrayList<Integer>) list.clone();
	     Collections.sort(sorted);
	     for(int i=0;i<list.size()-1;i++) {
	    	 for(int j=i+1;j<list.size();j++) {
	    		 @SuppressWarnings("unchecked")
				ArrayList<Integer> tmp =(ArrayList<Integer>) list.clone();
	    		 tmp.set(i, list.get(j));
	    		 tmp.set(j, list.get(i));
	    		 if(sorted.equals(tmp) || sorted.equals(list)) {
	    			 System.out.println("YES");
	    			 return ;
	    		 }

	    	 }

	     }
		 System.out.println("NO");
	}

}