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

if n >= 200:
    mx = 10**4
else:
    mx = sum(a) // 2

dp = [0] * (mx + 1)
dp[0] = 1
for i in a:
    for j in range(mx - 1, -1, -1):
        if i + j > mx:
            continue
        dp[j + i] += dp[j]
        dp[j + i] = min(dp[j + i], 2)
    # print(dp)

for i in range(mx + 1):
    if dp[i] >= 2:
        print(sum(a) - 2 * i if sum(a) - 2 * i else -1)
        exit()
print(-1)