Cambridge and Mansfield shared a 1-1 draw in Sky Bet League Two to leave both sides chasing the play-offs at Christmas.The Stags led after 23 minutes when Adam Chapman's long-range free kick caught out Sam Beasant.The goal saw Cambridge spring to life and they soon had a Luke Berry effort ruled out for offside before drawing themselves level nine minutes before half time.Ryan Donaldson, on as an early substitute, cut inside from the right wing and saw his effort from the edge of the box take a large deflection on its way past Brian Jensen.Jensen was then called on to deny Ben Williamson from a tight angle after the forward was released by Ryan Ledson's splendid pass, before Berry headed a Donaldson corner wide just before the interval.In a second half of few chances, Beasant twice preserved a point for Cambridge in the closing minutes, keeping out Matt Green after a Leon Legge error and then saving from Krystian Pearce from a corner in injury time.