import numpy as np

n = int(input())
A = list(map(int, input().split()))
DP = np.zeros(4000005, np.bool_)
DP[0] = 1
for i in range(n):
    DP[A[i]:] ^= DP[:-A[i]]

ans = 0
for i in range(1, 4000001):
    if DP[i]:
        ans ^= i
print(ans)