Lagrangian Dynamics - pendulum near a sphere?

Here's the problem. A simple pendulum (m m, string length r) is supported above a large uniform sphere of m M and radius R. L is the distance of the support of the pendulum from the halfway mark of the sphere. Write V in terms of theta, taking into account gravitational attraction of M and m. Approximate for small theta and L only slightly greater than R + r. Determine period of oscillation of motion. Neglect earth's gravitational field.