The bottom of a vent elbow is 60″ above the floor. It is tied into a common flue at 61 1/2″ above the floor. What is the length of the vent connector from the elbow to the common flue?

The bottom of a vent elbow is 60″ above the floor. It is tied into a common flue at 61 1/2″ above the floor. What is the length of the vent connector from the elbow to the common flue?