import sys
readline=sys.stdin.readline

N=int(readline())
A=map(int,readline().split())
dp=set()
dp.add(next(A))
for a in A:
    dp={i+a for i in dp}|{i-a for i in dp}|{i*a for i in dp}|({(-i)//a*(-1) for i in dp} if a>0 else set())
ans=max(dp)
print(ans)