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.math.BigDecimal;
import java.util.*;

public class Main {


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        sc.nextLine();
        String pStr = sc.nextLine();

        int[] p = new int[n];
        int[] temp = new int[n];
        for (int i = 0; i < n; i++) {
            p[i] = Integer.parseInt(pStr.split(" ")[i]);
            temp[i]  = Integer.parseInt(pStr.split(" ")[i]);
        }

        Arrays.sort(temp);

        boolean sorted = true;
        int before, after;
        before = after  = 0;
        for(int i = 0;i < n; i++){
            if(p[i] != temp[i]){
                sorted  = false;
                before = i;
                break;
            }
        }
        if(sorted){
            System.out.println("YES");
            return;
        }



        for(int i = n - 1; i >= 0; i--){
            if(p[i] != temp[i]){
                after = i;
                break;
            }
        }

        if(p[before] == temp[after] && p[after] == temp[before]){
            int t;
            t = p[after];
            p[after] = p[before];
            p[before] = t;
        }

        sorted = true;
        for(int i = 0;i < n; i++){
            if(p[i] != temp[i]){
                sorted  = false;
                break;
            }
        }
        if(sorted){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }

    }


}