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 Julia (0.5.0) (judge verdict: Accepted)

n=parse(Int,readline())
pn=readline()
pn1=split(pn)
X=Any[]
for i=1:n
    X= push!(X , parse(Int,pn1[i]))
end
Y=Any[]
for i=1:n
    Y= push!(Y , i)
end
for i=1:n
    if X[i]!=i
        a=X[i]
        X[i],X[a]=X[a],X[i]
        break
    end
end
k=0
for i=1:n
    if X[i]!=Y[i]
        k=k+1
    else
    end
end

if k==0
    print("YES")
else
    print("NO")
end