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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

fun main(vararg args: String) {
    val input = readLine()!!.split(" ")

    val n = input[0].toInt()
    val p = readLine()!!.split(" ").map(String::toInt)

    var count = 0

    for(i in 0 until n) {
        if(p[i] != i + 1) {
            val index = p[i] - 1
            if(p[index] == i + 1) {
                count++
            }else{
                count = -1
            }
        }
    }

    if(count == 0 || count == 2) {
        println("YES")
    }else{
        println("NO")
    }
}