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: Runtime Error)

function main(input)
{
    const args = input.split('\n');
    const numbers = args[1].split(' ').map(x => parseInt(x, 10));
    // console.log(numbers);

    let answers = [];
    for (var i = 0; i < numbers.length; i++)
    {
    	answers.push(i + 1);
    }

    // console.log(answers);

    let count = 0;
    for (var i = 0; i < numbers.length; i++)
    {
    	count += (answers[i] === numbers[i]) ? 0 : 1
    }
    // console.log(count);

    const answer = (count === 2 || count === 0) ? 'YES' : 'NO';
    console.log(answer);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));

// main(require("fs").readFileSync("/Users/hiroi_junki/IdeaProjects/atcoder/test_abc_135_b.txt", "utf8"));