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 N=0;
    int p[50]={};
    int count=0;
    int change=0;
    int max=0;
    scanf("%d",&N);

    for(int i=0;i<N;i++){
        scanf("%d",&p[i]);
    }

    for(int j=0;j<N;j++){
        max=0;
        for(int i=0;i<N;i++){
	    	if(max<p[i]){
	    		max=p[i];
		    	count=i;
		    }
	    }
        if(count==j){
            p[j]=0;
        }else{
            change ++;
            p[count]=p[j];
            p[j]=0;
        }
    }
    if(change<2){
        printf("YES\n");
    }else{
        printf("NO\n");
    }

    return 0;
}