Problem:
We have N cards numbered 1, 2, ..., N. Card i (1 \leq i \leq N) has an integer A_i written in red ink on one side and an integer B_i written in blue ink on the other side. Initially, these cards are arranged from left to right in the order from Card 1 to Card N, with the red numbers facing up.  Determine whether it is possible to have a non-decreasing sequence facing up from left to right (that is, for each i (1 \leq i \leq N - 1), the integer facing up on the (i+1)-th card from the left is not less than the integer facing up on the i-th card from the left) by repeating the operation below. If the answer is yes, find the minimum number of operations required to achieve it.    * Choose an integer i (1 \leq i \leq N - 1). Swap the i-th and (i+1)-th cards from the left, then flip these two cards.

Incorrect submission (verdict: Wrong Answer):
import sys
import itertools
import math

def first(i,a,b):
    if i%2==0: return [a,b]
    else: return [b,a]

def chk(a,b):
    if n%2==0:
        for i in range(m-1):
            if a[i][0]>b[i][0] or b[i][0]>a[i+1][0]:
                return 0
        if a[m-1][0]>b[m-1][0]: return 0
            
    else:
        for i in range(m-1):
            if a[i][0]>b[i][0] or b[i][0]>a[i+1][0]:
                return 0

    return 1

def cal(a,b):
    l=[]
    if n%2==0:
        for i in range(m):
            l+=[a[i][1],b[i][1]]
    if n%2==1:
        for i in range(m-1):
            l+=[a[i][1],b[i][1]]
        l.append(a[m-1][1])
    return l
        


n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
if n==1:
    print(0)
    sys.exit()

x=[first(i,a[i],b[i]) for i in range(n)]
x.sort()

m=math.ceil(n/2)
p=[i for i in range(n)]
ans=1000000

for q in list(itertools.combinations(p,m)):
    tmpa,tmpb=[],[]
    for i in range(n):
        if i in q: tmpa.append( [a[i],i] )
        else: tmpb.append([b[i],i])
    tmpb.sort()

    if chk(tmpa,tmpb)==1:
        s=[0 for i in range(n)]
        t=cal(tmpa,tmpb)
        tans=0
        for i in range(n-1):
            for j in range(1,n):
                if a[i]>a[j]: tans+=1
        ans=min(ans,tans)

print(ans//2 if ans<1000000 and ans%2==0 else -1)

Fixed, accepted submission:
import sys
import itertools
import math

def first(i,a,b):
    if i%2==0: return [a,b,i]
    else: return [b,a,i]

def chk(a,b):
    if m==l:
        for i in range(m-1):
            if a[i][0]>b[i][0] or b[i][0]>a[i+1][0]:
                return 0
        if a[m-1][0]>b[m-1][0]: return 0
            
    else:
        for i in range(l):
            if a[i][0]>b[i][0] or b[i][0]>a[i+1][0]:
                return 0

    return 1

def cal(a,b):
    w=[]
    if m==l:
        for i in range(l):
            w+=[a[i][1],b[i][1]]
    else:
        for i in range(l):
            w+=[a[i][1],b[i][1]]
        w.append(a[m-1][1])
    return w
        


n=int(input())
m,l=n-n//2,n//2
a=list(map(int,input().split()))
b=list(map(int,input().split()))
if n==1:
    print(0)
    sys.exit()

x=[first(i,a[i],b[i]) for i in range(n)]

p=[i for i in range(n)]
ans=1000000

for q in itertools.combinations(p,m):
    tmpa,tmpb=[],[]
    for i in range(n):
        if i in q: tmpa.append([ x[i][0],x[i][2] ])
        else: tmpb.append([x[i][1],x[i][2]])
    tmpa.sort()
    tmpb.sort()


    if chk(tmpa,tmpb)==1:
        t=cal(tmpa,tmpb)
        tans=0
        for i in range(n):
            for j in range(i):
                if t[j]>t[i]: tans+=1
        ans=min(ans,tans)

print(ans if ans<=n*(n-1)/2 else -1)