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 n = Integer.parseInt(sc.next());
    int p[] = new int[n];
    int pc[] = new int[n];
    int swapa = 0;
    int swapb = 0;
    int flg = 0;
    
    for (int i=0; i<n; i++){
      p[i] = Integer.parseInt(sc.next());
    }
    
    for (int i=0; i<n; i++){      
      swapa = p[i];
      
      for (int j=i; j<n; j++){
        for (int ii=0; ii<n; ii++){
          pc[ii] = p[ii];
      	}
        
        swapb = p[j];
        pc[j] = swapa;
        pc[i] = swapb;
        
        flg = 0;
        for (int k=0; k<n-1; k++){
          if (pc[k] > pc[k+1]) {
            flg++;
          }
        }
        if (flg==0){
          System.out.println("Yes");
          return;
        }
      }
    }

	System.out.println("No");


  }
}