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 (2.3.3) (judge verdict: Wrong Answer)

# require "enumerator"

N = gets

P = gets
P_arry = P.split(" ")

P_int = P_arry.map {|p|
    p.to_i
}

isBreak = false
failure_count = 0

if P_int.each_cons(2).all? {|a, b| a <= b }
    isBreak = true
    print "Yes"
    exit
end

for i in 0..N.to_i-1
    for j in 0..N.to_i-1
        if i >= j
            next
        end
        if P_int[i] > P_int[j]
            P_int[i],P_int[j] = P_int[j],P_int[i]
            if P_int.each_cons(2).all? {|a, b| a <= b }
                isBreak = true
                break
            else
                failure_count = failure_count + 1
                P_int[i],P_int[j] = P_int[j],P_int[i]
            end
        end
    end
    break if isBreak || (failure_count > 0)
end

if isBreak
    print "Yes"
else
    print "No"
end