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 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
void main()
{
    int i,k,x,n,j,flag=0,temp=0;
    scanf("%d",&n);
    int a[n];


    for (i=0; i<n; i++)
        {
            scanf("%d", &a[i]);
        }
    if (a[0]!=1)
    {
    for(i=1; i<n; i++)
    {
        if(a[i] == 1)
        {
            break;
        }
    }

        x=a[0];
        a[0]=a[i];
        a[i]=x;
    }
  else
    {
    for(j=0; j<n; j++)
    {
        if(a[j]!=j+1)
        {
            flag=1;
            break;
        }
    }
    for(k=0;k<n;k++)
    {
        if(a[k]==k+1)
        {
            break;
        }
    }
    if (flag==1)
    {
        x=a[j];
        a[j]=a[k];
        a[k]=x;
    }

    }
    for(i=0; i<n ; i++)
    { if(a[i]>a[i+1])

    {
            printf("NO");
            temp=1;
            break;
    }
    }
    if (temp==0)
    printf("YES");
}