N = int(input())

dp = [[0] * 2 for _ in range(N)]
inputs = map(int, input().split())

for i, val in enumerate(inputs):
    if i == 0:
        dp[i][0] = 0
        dp[i][1] = val
    else:
        dp[i][0] = max(dp[i - 1])
        dp[i][1] = dp[i - 1][0] + val
        
print(max(dp[N-1]))