fn main() {
  let mut s1 = "Hi".to_string();
  let s2 = String::from("there");
  let s3;

  s1.push_str(", ");
  println!("S1: {}", s1);
  println!("S2: {}", s2);

  s3 = s1 + &s2;

  println!("S3: {}", s3)
}