import sys

input = sys.stdin.buffer.readline

n = int(input())
A = list(map(int, input().split()))

temp = 1

for a in A:
    nx = temp << a
    # print("temp", bin(temp), "nx", bin(nx))
    temp ^= nx

# ans = 0
# keta = 0
# while temp:
#     if temp % 2:
#         ans ^= keta
#     temp //= 2
#     keta += 1
binary = bin(temp)[2:]
ans = 0
for i in range(len(binary)):
    if binary[len(binary) - i - 1] == "1":
        ans ^= i

print(ans)