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>

int sorted(int a[],int size);

int main()
{
    int n;
    scanf("%d",&n);
    int arr[n];
    for(int i=0; i<n; i++)
    {
        scanf("%d",&arr[i]);
    }
    int s = sorted(arr,n);
    if(s==1)
    {
        printf("YES");
    }
    else
    {
        int i=0,j=1,flag=0;
        while(i!=(n-1))
        {
            while(j!=n)
            {
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                s = sorted(arr,n);
                if(s==1)
                {
                    flag = 1;
                    break;
                }
                temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                j++;
            }
            if(flag==1)
            {
                break;
            }
            i++;
        }
        if(flag==1)
        {
            printf("YES");
        }
        else
        {
            printf("NO");
        }
    }
}

int sorted(int a[],int size)
{
    int i=0,j=1,flag=1;
    while(i!=(size-1))
    {
        int min = a[i];
        while(j!=size)
        {
            if(a[j]<min)
            {
                flag = 0;
                break;
            }
            j++;
        }
        if(flag==0)
        {
            break;
        }
        i++;
    }
    return flag;
}