So what's YOUR question?
Mine is "Why haven't you read the intro posts on how to use code tags?"
Tricky question Salem; hard to answer. Could you make it a multiple choice one?
a) Because I am too busy to read any rule and beside, they are not that important. b) Because I have a sense of entitlement and know my worth. c) Because rules do not apply to me. d) Because I am a newbie and people surely will have pity of me and cut me some slack. e) All the above.
Nope, [s]he didn't mean that correction.
main() always returns an int as long as it is part of an operating system, therefore it should be int main ( void ) in this case, and care should put to finish the function with the statement return [status]. printf("Multiples of %d and %d are %d",m,n,o); You took the liberty of adding artifact to it, but not fix the ugly format that not including a '\n' at the end of the literal string in printf will originate.
Furthermore, if you choose to not carry return the cursor after each printf(), a call to fflush( stdout ) is a prudent statement to incorporate afterward.