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 C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main()
{
   int n,i,j,t,arr[50],flag=0;
   scanf("%d",&n);
   for(i=0;i<n;i++)
   {
       scanf("%d",&arr[i]);
   }
   for(i=0,j=n-1;i<=n/2;i++,j--)
   {


           if(arr[i]>arr[j])
           {
                t=arr[i];
                arr[i]=arr[j];
                arr[j]=t;

           }

   }
    for(i=0;i<n;i++)
   {
       for(j=i+1;j<n;j++)
       {
           if(arr[i]>arr[j])
           {
               flag=1;
                break;
           }
       }
   }
   if(flag==0)
   {
       printf("YES\n");
   }
   else
   {
       printf("NO\n");
   }
}