old_centers = [[(h - l) * random.random() + l for (l, h) in borders]
for _ in range(k)]
clusters, centers = next_step(old_centers, data)
old_centers = [[(h - l) * random.random() + l for (l, h) in borders]
for _ in range(k)]
clusters, centers = next_step(old_centers, data)