Problem:
In CODE FESTIVAL XXXX, there are N+1 participants from all over the world, including Takahashi.  Takahashi checked and found that the _time gap_ (defined below) between the local times in his city and the i-th person's city was D_i hours. The time gap between two cities is defined as follows. For two cities A and B, if the local time in city B is d o'clock at the moment when the local time in city A is 0 o'clock, then the time gap between these two cities is defined to be min(d,24-d) hours. Here, we are using 24-hour notation. That is, the local time in the i-th person's city is either d o'clock or 24-d o'clock at the moment when the local time in Takahashi's city is 0 o'clock, for example.  Then, for each pair of two people chosen from the N+1 people, he wrote out the time gap between their cities. Let the smallest time gap among them be s hours.  Find the maximum possible value of s.

Incorrect submission (verdict: Wrong Answer):
#time gap
n=int(input())
lists=list(map(int,input().split()))
if n>24:
    print(0)
else:
    timelist=[0 for i in range(13)]
    
    for i in lists:
        timelist[i]+=1
    flag=True
    for j in range(13):
        if j==0 or j==12:
            if timelist[j]>1:
                flag=False
        else:
            if timelist[j]>2:
                flag=False
    if flag:
        uselist1=[]
        uselist2_=[]
        for i in range(13):
            if timelist[i]==1:
                uselist1.append((i))
            if timelist[i]==2:
                uselist2_.append((i))
            else:
                continue
        uselist2=[]
        for j in uselist2_:
            uselist2.append(j)
            uselist2.append(24-j)
        lens=len(uselist1)
        mini=100
        for i in range(2**lens):
            sublist=[]
            sublist=sublist+uselist2
            j=format(i,"0%ib"%lens)
            for k in range(lens):
                if j[k]=="0":
                    sublist.append(uselist1[k])
                else:
                    sublist.append(24-uselist1[k])
            sublist=sorted(sublist)

            lenss=len(sublist)
            for k in range(1,lenss):
                mini=min(mini,sublist[k]-sublist[k-1])
        if   n==1:
            print(lists[0])
        else:
            print(mini)
    if not flag:
        print(0)

Fixed, accepted submission:
#time gap
n=int(input())
lists=list(map(int,input().split()))
if n>24:
    print(0)
else:
    timelist=[0 for i in range(13)]
    
    for i in lists:
        timelist[i]+=1
    flag=True
    for j in range(13):
        if j==0:
            if timelist[j]>0:
                flag=False
        else:
            if timelist[j]>2:
                flag=False
    if flag:
        uselist1=[]
        uselist2_=[]
        for i in range(13):
            if timelist[i]==1:
                uselist1.append((i))
            if timelist[i]==2:
                uselist2_.append((i))
            else:
                continue
        uselist2=[]
        for j in uselist2_:
            uselist2.append(j)
            uselist2.append(24-j)
        uselist2=list(set(uselist2))
        lens=len(uselist1)
        minilist=[]
        for i in range(2**lens):
            sublist=[0]
            mini=100
            sublist=sublist+uselist2
            j=format(i,"0%ib"%lens)
            for k in range(lens):
                if j[k]=="0":
                    sublist.append(uselist1[k])
                else:
                    sublist.append(24-uselist1[k])
            sublists=sorted(sublist)
            lenss=len(sublists)
            for k in range(1,lenss):
                mini=min(mini,sublists[k]-sublists[k-1])
            mini=min(mini,24-sublists[-1],sublists[-1])
            minilist.append(mini)  
        else:
            print(max(minilist))
    if not flag:
        print(0)