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: Accepted)

#include<stdio.h>
#include<stdlib.h>
int cmpfunc (const void * a, const void * b) {
   return ( *(int*)a - *(int*)b );
}


int main(void){
        int i,j,a[50],n,b[50],k=0,t=0,s=0;

        scanf("%d",&n);

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

        qsort(b, n, sizeof(int), cmpfunc);

        for(i=0;i<n;i++){
            if(b[i]!=a[i]){
                s++;
            }
        }

        if(s==0 || s==2){
            printf("YES");
        }
        else{
            printf("NO");
        }

        return 0;
}