from collections import*
n=int(input())
d=defaultdict(lambda:-1<<60)
d[0]=0
r=0
a=[*map(int,input().split())]
s=sum(a)
for i in a:
    s-=i
    p=defaultdict(lambda:-1<<60)
    r=max(d[i]+s,d[-i]+s,r)
    for j in d:
        p[j]=max(p[j],d[j]+i)
        p[j+i]=max(p[j+i],d[j])
        p[j-i]=max(p[j-i],d[j])
    d=p
    del p
print(r if r else -1)