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) {
		Scanner scn=new Scanner(System.in);
		ArrayList<Integer> list=new ArrayList<>();
		ArrayList<Integer> list1=new ArrayList<>();
		
		int t=scn.nextInt();
		
		for(int i=0;i<t;i++) {
			int x=scn.nextInt();
			
			list.add(x);
			list1.add(x);
		}
		Collections.sort(list);
		
		int count=0;
		for(int i=0;i<list.size();i++) {
			
			if(list.get(i)!=list1.get(i)) {
				count++;
				if(count>3) {
					break;
				}
			}		
		}
		if(count<3) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
		scn.close();
	}
}