def solve(ratings):
    if len(ratings) == 1:
        return ratings[0]

    nonskipped = ratings[0]
    skipped = 0

    for i in range(1, len(ratings)):
        tmp = skipped
        skipped = nonskipped
        nonskipped = max(nonskipped, tmp) + ratings[i]

    return max(nonskipped, skipped)

def main():
    print(solve([1, 2, 3, 4, -10]))
    print(solve([6, -1, -2, -3, -10]))
    print(solve([6, -1, -8]))

main()