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: Wrong Answer)

import java.util.*;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        int[] ar = new int[num];
        for(int i=0;i<ar.length;i++)
        {
            ar[i]=sc.nextInt();
        }
        int front=-1,back=-1;
        int agad=ar[0];
        for(int i=1;i<ar.length-1;i++)
        {
            if(ar[i]>ar[i-1] && ar[i]>ar[i+1])
                front = i;
            if(ar[i]<ar[i-1] && ar[i]<ar[i+1])
                back = i;
        }
        if(front==-1)
        {
            if(ar[0]>ar[1])
                front=0;
        }
            
        if(back==-1)
        {
            if(ar[ar.length-1]<ar[ar.length-2])
                back=ar.length-1;
        }
        if(front==-1)
        {
            System.out.println("YES");
        }
        else
        {
        int temp = ar[front];
        ar[front]=ar[back];
        ar[back]=temp;
        int flag=0;
        for(int i=0;i<ar.length-1;i++)
        {
            if(ar[i]>ar[i+1])
            {
                flag=1;
                System.out.println("NO");
                break;
            }
        }
        if(flag==0)
        System.out.println("YES");
    }
    }
}