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.io.PrintWriter;
import java.util.*;

public class Main {
		public static void main(String[] args) {
			Scanner stdin = new Scanner(System.in);
			PrintWriter out = new PrintWriter(System.out);
			
			int N = Integer.parseInt(stdin.next());
			int p[] = new int[N];
			int min = 50;
			int mini = 0;
			int max = 0;
			int maxi = 0;
			
			for(int i=0;i<N;i++) {
				p[i] = Integer.parseInt(stdin.next());
				if(min>p[i]) {
					min=p[i];
					mini=i;
				}
				if(max<p[i]) {
					max=p[i];
					maxi=i;
				}
			}
			
			int flag = 0;
			
			for(int i=0;i<N-1;i++) {
				if(p[i] <=p[i+1]) {
					flag = 1;
				}
				else {
					int sub = p[maxi];
					p[maxi] = p[mini];
					p[mini] = sub;
					for(int z=0;z<N-1;z++) {
						if(p[z] <=p[z+1]) {
							flag = 1;
						}
						else {
							flag=0;
							break;
						}
					}
					break;
				}
			}
			if(flag==1) {
				out.print("Yes");
			}
			else {
				out.print("No");
			}
			
			out.flush();
	}
}