n = int(input())
v = list(map(int,input().split()))
dp = [[0] * (n + 1) for _ in range(2)]
for i in range(n):
    dp[1][i+1] = dp[0][i] + v[i]
    dp[0][i+1] = max(dp[0][i],dp[1][i])
print(max(dp[0][-1],dp[1][-1]))