Need help with velocity in circular motion?

A light rigid rod is 77.2 cm long. Its top end is pivoted on a low-friction horizontal axle. The rod hangs straight down at rest, with a small mive ball attached to its bottom end. You strike the ball, suddenly giving it a horizontal velocity so that it swings around in a full circle. What minimum speed at the bottom is required to make the ball go over the top of the circle?