fn main() {
   let x = "hi";
   let y = "world";
   let z = "b".to_string();

   let res: &'static str = longest(x, y, &z);

   println!("{}", res);
}

// change z to &'b str to make this work
fn longest<'a, 'b>(x: &'a str, y: &'a str, z: &'a str) -> &'a str {
    println!("{}", z);
    if x.len() > y.len() {
        x
    } else {
        y
    }
}