def best_list_pureness(*args):
    def calculate_p(p_lst):
        p = 0
        for idx in range(len(p_lst)):
            p += p_lst[idx] * idx
        return p

    lst = args[0]
    k = args[-1]
    best_rotations = 0
    best_pureness = 0
    best_pureness = calculate_p(lst)
    for i in range(k):
        lst.insert(0, lst.pop())
        current_pureness = calculate_p(lst)
        if current_pureness > best_pureness:
            best_pureness = current_pureness
            best_rotations = i + 1

    return f"Best pureness {best_pureness} after {best_rotations } rotations"


test = ([4, 3, 2, 6], 4)
result = best_list_pureness(*test)
print(result)

test = ([7, 9, 2, 5, 3, 4], 3)
result = best_list_pureness(*test)
print(result)

test = ([1, 2, 3, 4, 5], 10)
result = best_list_pureness(*test)
print(result)