What is this asking - bug in input field

Question

the actual question should be easy however i cannot directly understand how to fill it out it wont allow the addition sign. i took a screenshot to show but cannot add it to question. this just seems like a bug.

Answer 1

You cannot insert images in post, but you can host them somewhere on internet and provide the link... but better to copy-paste your code in a playground project and share here the link ^^

Answer 2

please show your code