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: Accepted)

/* ABC135-B.c
   Takatan */

#include<stdio.h>
#include<stdlib.h>
int main(void){
    int number, *array, change, i;
    change = 0;

    scanf( "%d" , &number);

    array = malloc(sizeof(int) * number);

    for(i=0; i < number; i++){
        scanf( "%d" , array+i);
        if(array[i]!=i+1){
            if(change==0){
                change = array[i];
            }else{
                if(change!=i+1){
                    printf( "NO\n" );
                    return 0;
                }
            }
        }
    }

    printf( "YES\n" );
    return 0;
}