N = int(input())
A = list(map(int,input().split()))
dp = 1 << A[0]
dp |= 1
for i in range(1,N):
    dp = (dp << A[i]) ^ dp
ans = 0
for i in range(1,sum(A)+1):
    dp >>= 1
    if dp & 1:
        ans ^= i
print(ans)