import sys
readline=sys.stdin.readline

N=int(readline())
A=list(map(int,readline().split()))
dp=set()
dp.add(A[0])
for a in A[1:]:
    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)