n=int(input())
d=[int(p) for p in input().strip().split(' ')]
f1=[0 for _ in range(n)]
f1[0]=d[0]
f2=[0 for _ in range(n)]
f2[-1]=d[-1]
for i in range(1,n):
    f1[i]=max(f1[i-1],0)+d[i]
for i in range(1,n):
    f1[i]=max(f1[i-1],f1[i])
for i in range(-2,-(n+1),-1):
    f2[i]=max(f2[i+1],0)+d[i]
for i in range(-2,-n-1,-1):
    f2[i]=max(f2[i+1],f2[i])
ans=f1[0]+f2[2]
for i in range(2,n-1):
    ans=max(ans,f1[i-1]+f2[i+1])
print(ans)