Raab Game II

Consider a two player game where each player has n cards numbered 1,2,\dots,n. On each turn both players place one of their cards on the table. The player who placed the higher card gets one point. If the cards are equal, neither player gets a point. The game continues until all cards have been played. You are given the number of cards n and the players' scores at the end of the game, a and b. Yo