def get_rotation_matrix(axis_name, theta):
    matrices = {
        "x":
            [[1, 0, 0],
            [0, cos(theta), -sin(theta)],
            [0, sin(theta), cos(theta)]],
        "y":
            [[cos(theta), 0, sin(theta)],
            [0, 1, 0],
            [-sin(theta), 0, cos(theta)]],
        "z":
            [[cos(theta), -sin(theta), 0],
            [sin(theta), cos(theta), 0],
            [0, 0, 1]]
    }
    return matrices[axis_name]

def matmul(a, b):
    n = len(a)
    m = len(b)
    assert len(a[0]) == m
    p = len(b[0])
    c = []
    for i in range(n):
        row = []
        for j in range(p):
            row.append(sum(a[i][k]*b[k][j] for k in range(m)))
        c.append(row)
    return c