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
    S += a
ans = 0
for i in range(1,S+1):
    dp >>= 1
    if dp & 1:
        ans ^= i
print(ans)