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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
  "fmt"
)

func main(){
  var N, change int
  var p [50] int
  
  fmt.Scan(&N)
  change = 0
  for i := 0; i < N; i ++ {
    fmt.Scan(&p[i])
  }
  for i := 1; i < N; i ++ {
    if p[i - 1] >= p[i]{
      change = change + 1
    }
  }
  for i := 0; i < N; i ++ {
    for n := 0; n < N; n ++ {
      if p[n] == p[i] {
        change = change + 1
      }
    }
  }
  if change < 3 {
    fmt.Print("YES")
  }else{
    fmt.Print("No")
  }
}