You are helping a dance studio build a new online registration system.
This studio hosts classes in the evening to teach people how to dance. Groups of friends will sign up to come together for a class.
In order to learn to dance, the group must have an even number of people. This allows the group to divide evenly for styles like square dancing and contra dancing.
Write a function that counts up the total number of people who can participate each evening. You will be given the number of people in each of four groups:
Groups that tried to sign up with an odd number of people will not be allowed to come. Add up only the groups that have an even number of people and return the total as your result.