n = int(input())
A = list(map(int, input().split()))
bit = 1
for a in A:
    bit ^= bit << a

i = 1
ans = 0
bi = bin(bit)[2:][::-1]
l = len(bi)
for i in range(1, l):
    if bi[i] == "1":
        ans ^= i
print(ans)