from functools import reduce


def vector_items(vec):
    vec_iter = iter(vec)
    while True:
        val, n = next(vec_iter), next(vec_iter)
        for _ in range(n):
            yield val


def scalar_product(vec1, vec2):
    return reduce(lambda acc, i: acc + i[0] * i[1],
                  zip(vector_items(vec1), vector_items(vec2)),
                  0)

if __name__ == "__main__":
    first_list = [1, 4, 3, 4, 5, 3, 1, 5]
    second_list = [3, 5, 4, 6, 5, 5]
    print(scalar_product(first_list, second_list))