import os,sys,random,threading
from random import randint
from types import GeneratorType
from functools import lru_cache
from bisect import bisect_left,bisect_right
from collections import Counter,defaultdict,deque
from itertools import accumulate,combinations,permutations
from heapq import  heapify,heappop,heappush
from typing import Generic,Iterable,Iterator,TypeVar,Union,List
from math import sqrt,log,log10,log2
from sys import stdin, stdout, setrecursionlimit
input = lambda: sys.stdin.readline().rstrip("\r\n")
MI = lambda :map(int,input().split())
li = lambda :list(MI())
ii = lambda :int(input())
inf=1<<60




n=ii()

a=li()

f=0

for x in a:
    tmp=(f<<x)^(1<<x)
    f^=tmp

res=0

f=bin(f)[2:][::-1]

for i in range(1,len(f)):
    if f[i]=="1":
        res^=i

print(res)