Counting beers

Nakov is keen football fаn and he is passionate about the upcoming FIFA
World Cup tournament. A month before the tournament Nakov started his
preparations with a few stacks of beer and a few single beer bottles.
You are given a list of Nakov's stacks and Nakov's single beers. Help
him to count how many stacks of beer and how many additional single
bottles he has for the tournament. Assume that a stack of beer holds 20
beers.