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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input) {
    input = input.split("\n");
    N = Number(input[0])
    tmp = input[1].split(" ");
    an = 0;
    for(i = 1; i <= N; i++){
        tmp.push(Number(tmp[0]));
        tmp.shift();
    }
    for(j = 1; j <= N; j++){
        inj = tmp[j];
        if(inj == j) continue;
        tmp = swap(tmp,inj,j);
        an++;
    }
    console.log((an < 2) ? "YES" : "NO");
}
function swap(a,x,y){
    a[x]=[a[y],a[y]=a[x]][0];
    return a;
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));