Warren and Naida make a list of numbers. They start with 0, then Warren adds 20, then
Naida minus 1, then Warren plus 19, then Naida minus 2.
0, 20, 19, 38, 36 ,. . .
This pattern continues until Warren adds 1 and Naida subtracts 20, resulting in
at 0. The largest number on their list is 55 because 38+36+1-20