def main():
    n = int(input())
    A = list(map(int, input().split()))
    N = 10**5
    inf = 1<<60
    dp = [inf] * (2*N+1)
    a = A[0]
    dp[a] = a
    dp[-a] = a
    for a in A[1:]:
        ndp = dp[:]
        for b in range(-N, N+1):
            if -N <= b-a:
                ndp[b-a] = min(ndp[b-a], dp[b]+a)
            if b+a <= N:
                ndp[b+a] = min(ndp[b+a], dp[b]+a)
        dp = ndp
        #print(dp[-10:] + ["OK"] + dp[:10])
    ans = dp[0]
    if ans < inf and ans != sum(A):
        return sum(A)-ans
    else:
        return -1
print(main())