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 Ruby (2.7.1) (judge verdict: Wrong Answer)

n = gets.to_i
p_arr = gets.split.map(&:to_i)
reorder_cnt = 0
reo = nil
reo_af = nil

prev = p_arr[0]
n.times do |i|
  if p_arr[i] < prev
    reorder_cnt += 1
    if reorder_cnt == 1
      reo = prev
      reo_af = p_arr[i]
    elsif reorder_cnt == 2
      if reo < prev || reo_af < p_arr[i]
        puts 'NO'
        exit
      else
        prev = reo
        next
      end
    else
      puts 'NO'
      exit
    end
  end
  prev = p_arr[i]
end
puts 'YES'