use std::collections::HashSet;
use std::rc::Rc;

fn main() {
  let a: HashSet<Rc<String>> = HashSet::new();
  let mut b: HashSet<Rc<String>> = HashSet::new();
  b.insert(Rc::new(format!("OI")));
  let c = a.union(&b);
  let d: HashSet<Rc<String>> = c.collect();

  for i in d.iter() {
    println!("{}",i);
  }
}