My code has issues...?

Oooookie dokie, so i've been coding in JAVA for almost two years, and this isn't that, but I easily understand this. Basically, you aren't storing the input as "int num". The program won't be able to use "num" without declaring the value of it first. You should also declare k as something, even if it's 0. I don't know exactly how the prime number checker works in terms of syntax, but I don't know how you call the "getchar()" method without creating it and putting code in it. Sorry if I'm no help, but remember.... I know JAVA