N = int(input())
A = list(map(int, input().split()))
dp = [[0, 0] for i in range(N)]

for i in range(N):
    if i == 0:
        dp[i][0] = 0
        dp[i][1] = A[i]
    else:
        dp[i][0] = max(dp[i-1])
        dp[i][1] = dp[i-1][0]+A[i]

print(max(dp[N-1]))