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
print(ans)