n = int(input())
a = list(map(int,input().split()))
dp = [0]*n
dp[n-1]=a[n-1]
res = a[n-1]
for i in range(n-2,-1,-1):
    if dp[i+1]>0:
        dp[i]=dp[i+1]+a[i]
    else:
        dp[i]=a[i]
    res = max(res,dp[i])
print(res)

注意倒序遍历时的起止条件