def always_using_comprehensions(a, b, n):
    """matrix product of a, b of length n x n"""
    c = [
        sum(a[n * i + k] * b[n * k + j] for k in range(n))
        for i in range(n)
        for j in range(n)
    ]

    c = []
    for i in range(n):
        for j in range(n):
            ij_entry = sum(a[n * i + k] * b[n * k + j] for k in range(n))
            c.append(ij_entry)

    return c