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: Accepted)

import java.util.Scanner
import java.util.ArrayList

fun main(args: Array<String>){
    val sc = Scanner(System.`in`)
    val N = sc.nextInt()

    var arraylist = ArrayList<Int>()
    for(i in 0 until N){
       arraylist.add(sc.nextInt())
    }

    var mani_flag = false
    var mani_index : Int
    var imp_flag = false
    for(i in 0 until N-1){
       if(arraylist.elementAt(i) > arraylist.elementAt(i+1)){
           if(mani_flag){
               imp_flag = true
               break
           }else{
               var nowmin = arraylist.elementAt(i+1)
               mani_index = i+1
                for(j in i+2 until N){
                    if(arraylist.elementAt(j) < nowmin){
                        nowmin = arraylist.elementAt(j)
                        mani_index = j
                    }
                }
               val tmp = arraylist.elementAt(i)
               arraylist.removeAt(i)
               arraylist.add(i, nowmin)
               arraylist.removeAt(mani_index)
               arraylist.add(mani_index, tmp)
               mani_flag = true
           }
       }
    }
    for(i in 0 until N - 1){
        if(arraylist.elementAt(i) > arraylist.elementAt(i+1)){
            imp_flag = true
        }
    }
    if(imp_flag){
        println("NO")
    }else{
        println("YES")
    }
}