To "input" numbers up to 20, you need to change first line to:

>>> a = [1,2,3,4,5,6,7,8,9,10, 11,12,13,14,15,16,17,18,19,20]

Because you aren't really trying.

Maybe if you take off your shoes you could use your toes.

Thank you if you tried or have anwsered!!