Compilare: warning: unused variable: `n` --> main.rs:10:9 | 10 | let n = it.next().unwrap().parse::<usize>().unwrap(); | ^ help: if this is intentional, prefix it with an underscore: `_n` | = note: `#[warn(unused_variables)]` on by default warning: unused variable: `c` --> main.rs:17:13 | 17 | let c = match h.get(&key) { | ^ help: if this is intentional, prefix it with an underscore: `_c` warning: variable does not need to be mutable --> main.rs:13:9 | 13 | let mut h = HashMap::<u32, u32>::new(); | ----^ | | | help: remove this `mut` | = note: `#[warn(unused_mut)]` on by default warning: 3 warnings emitted