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 main()
{
    int i,j,k,flag,x,term=0;
    scanf("%d",&k);
    int n[k];
    for(i=0; i<k; i++)
    {
        scanf("%d",&n[i]);
    }
    for(i=0; i<k; i++)
    {
        if(n[i]!=i+1)
        {
            flag=1;
            break;
        }
    }
    for(j=0; j<k; j++)
    {
        if(n[j]==i+1)
        {
            break;
        }
    }
    if(flag==1)
    {
        x=n[i];
        n[i]=n[j];
        n[j]=x;
    }
    for(i=0; i<k-1; i++)
    {
        if(n[i]>n[i+1])
        {
            printf("No\n");
            term=1;
            break;
        }
    }
    if(term==0)
    {
        printf("YES\n");
    }
    return 0;
}