warning: unused result which must be used, #[warn(unused_must_use)] on by default
  --> /in/foo.rs:48:5
   |
48 |     io::stdin().read_line(&mut buf);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: unused result which must be used, #[warn(unused_must_use)] on by default
  --> /in/foo.rs:54:13
   |
54 |             io::stdin().read_line(&mut buf);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: unused result which must be used, #[warn(unused_must_use)] on by default
  --> /in/foo.rs:62:13
   |
62 |             io::stdin().read_line(&mut buf);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^