In a tennis club, the lockers are placed side by side and are numbered from 1 to 40.
A membership of greater than three years means the locker is tagged with a red tag. A member who is a pro has his locker tagged with a green tag. It was found that every third locker is marked with a red tag and every fourth locker is marked with a green tag. Some lockers have both tags.
Which locker will be the first to represent a member who has been with the club more than three years and is a pro?