1  fn main() {
 2      let mut s = String::from("hello");
 3  
 4      let r1 = &s; // no problem
 5      let r2 = &s; // no problem
 6      println!("{} and {}", r1, r2);
 7      // variables r1 and r2 will not be used after this point
 8  
 9      let r3 = &mut s; // no problem
10      println!("{}", r3);
11  }
12