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;
int i,j;
int count=0;
int dummy;

scanf("%d",&n);

int p[n];

for(i=0;i<n;i++){
    scanf("%d",&p[i]);
}
for(i=1;i<n;i++){
    if(p[i]==1){
        dummy=p[0];
        p[0]=p[i];
        p[i]=dummy;
        break;
    }
}
for(i=0;i<n;i++){
    if(p[i]!=i+1){
        count++;
    }
}
/* for(i=0;i<n;i++){
    //printf("%d\n",p[i]);
}
for(i=0;i<n;i++){
    for(j=i+1;j<n;j++){
        if(p[i]>p[j]){
            dummy=p[i];
            p[i]=p[j];
            p[j]=dummy;
            count++;
            //printf("感としましt");
        }
    }
}*/
if(count==0||count==1)
printf("YES");
else
printf("NO");

return 0;

}