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: Accepted)

// inputに入力データ全体が入る
function Main(input) {
	// 1行目がinput[0], 2行目がinput[1], …に入る
    input = input.split("\n");
    // 数値の配列を作る
    const numList0 = input[0].split(' ').map(x => parseInt(x, 10));
    const N = numList0[0];
    const pList = input[1].split(' ').map(x => parseInt(x, 10));

    var count = 0;
    for (var i = 0; i < N; i++) {
        if (i + 1 !== pList[i]) {
            count++;
        }
        if (count > 2) {
            break;
        }
    }

    if (count <= 2) {
        console.log('YES');
    } else {
        console.log('NO');
    }
}
 
Main(require("fs").readFileSync("/dev/stdin", "utf8"));