def sushi_max(V):
    s_max2 = 0
    s_max = V[0]
    
    for i in range(1, len(V)):
        if (s_max2 + V[i]) > s_max:
            s_max, s_max2 = s_max2 + V[i], s_max
        else:
            s_max2 = s_max
            
    return s_max

N = int(input())
sara = list(map(int, input().split()))
print(sushi_max(sara))