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 cnt = 0;
        int num = sc.nextInt();
        List<Integer> alist = new ArrayList<Integer>();
        for(int i = 0; i < num;i++) {
        	alist.add(sc.nextInt());
        }
        
	List<Integer> list = new ArrayList<Integer>();
	for(int i = 0;i < num;i++) {
		list.add(i);
	}
	for(int a : alist){
        for(int b : list){
            if(a==b){
                cnt+=1;
                break;
            }
        }
    }
	if(num - cnt < 2 || num == cnt) {
		System.out.println("YES");
	}else {
		System.out.println("NO");
	}
	
	}
}