Need help with making my function work

Question

Function cannot read value and I don’t know how to fix this
Code:

https://code.sololearn.com/WJSG9f5kAVnz/?ref=app

Answer 1

Elements id was different in html its starts from Capital letter but in JS it was with small letter

https://code.sololearn.com/WrVvbslKijsX/?ref=app

Answer 2

Thank you!