$ cat captain-bruce.py 
nom = int(input())
members = list(map(int, input().split()))
rooms = set()   # Contains all the rooms.
room_more_mem = set()   # Contains only the rooms with families.

for m in members:
    if m not in rooms:
        rooms.add(m)
    else:
        room_more_mem.add(m)
print(rooms.difference(room_more_mem).pop())
$ cat captain-bruce-ver2.py 
nom = int(input())
members = list(map(int, input().split()))
rooms = set()   # Contains all the rooms.
room_more_mem = set()   # Contains only the rooms with families.

for m in members:
    if m not in room_more_mem:
        target = room_more_mem if m in rooms else rooms
        target.add(m)
print(rooms.difference(room_more_mem).pop())
$ cat captain-tigran.py 
k = int(input())
numbers = list(map(int, input().split()))
numset = set(numbers)
print(((sum(numset)*k)-(sum(numbers)))//(k-1))
$ time python3 captain-tigran.py < input01.txt 
2710

real	0m0.628s
user	0m0.552s
sys	0m0.076s
$ time python3 captain-bruce.py < input01.txt 
2710

real	0m1.006s
user	0m0.957s
sys	0m0.048s
$ time python3 captain-bruce-ver2.py < input01.txt 
2710

real	0m0.750s
user	0m0.686s
sys	0m0.064s