Need help answering

A horse salesman goes to an auction with a certain amount of horses. He sell half of all his horses plus half a horse to the first bidder, He sells hafe of what he had lft plus hafe a horse to the second bidder, and sells hafe what he has left plus hafe a horse to the final bidder. All three bidders get whole horses,and he has none left when he leaves how many horses did he start with?