import sys
rr = sys.stdin

N = int(rr.readline())
A = list(map(int,rr.readline().split()))

dp = 1
#S = 0
for a in A:
    dp ^= (dp << a)
    #dp = dp << a ^ dp
    #S += a
ans = 0
mask = 1

T = bin(dp)
for i in range(1,len(T)-2):
    if T[-1-i] == "1":
        ans ^= i
print(ans)