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(void)
{
        int n,i,j,c,s,min,index;

        scanf("%d",&n);

        int p[n];

        for(i=0;i<n;i++)
                scanf("%d",&p[i]);

        c=0;
        for(i=0;i<n;i++){
                min=p[i];index=i;s=0;
                for(j=i+1;j<n;j++){
                        if(min>p[j]){
                                min=p[j];index=j;s++;
                        }
                }
                p[index]=p[i];
                p[i]=min;
                if(s>0) c++;
        }

        if(c<=1) printf("Yes");
        else     printf("No");

        return 0;
}