N = int(input())
A = list(map(int, input().split()))

INF = 1<<60

MAX = 5000
if N <= 20:
    MAX *= N
elif N <= 200:
    MAX *= 10
else:
    MAX *= 2
dp = [INF]*(MAX*2+1)
dp[MAX] = 0
ans = INF
for i in range(N):
    ndp = [INF]*(MAX*2+1)
    for j in range(MAX*2+1):
        if dp[j] == INF: continue
        ndp[j] = min(ndp[j], dp[j])
        if j+A[i] <= MAX*2:
            if j+A[i] == MAX:
                ans = min(ans, dp[j]+A[i])
            ndp[j+A[i]] = min(ndp[j+A[i]], dp[j]+A[i])
        if A[i] <= j:
            if j-A[i] == MAX:
                ans = min(ans, dp[j])
            ndp[j-A[i]] = min(ndp[j-A[i]], dp[j])
    dp = ndp

if ans < (sum(A)+1)//2:
    print(sum(A)-ans*2)
else:
    print(-1)