Need help pls

Question

I wrote a code in c and on running it did work, it seems it need some input and i do not understand
https://code.sololearn.com/c5T6SbSa4rZJ/?ref=app

Answer 1

You need to use double quotes instead of single quotes

Answer 2

Strings in C must be enclosed between double quotes "... Sibgle quotes are needed only for chars like 'c'