What is the answer NNaNNaNNA?

Question

Hi!

I made a code on the addition and the result is NNaNNaNNaNNa... Please advise how to fix the code.
https://code.sololearn.com/Waq3S55vSa9e/?ref=app

Answer 1

NaN means not a number
Don't give two '+' in document.write
document.write(i+"<br>") ;

Answer 2

vv@msi😏😏 Thank you!