#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let line = "1\n2\n3\n4\n";
    for num in line.lines() {
        match num.parse::<i32>().map(|i| i * 2) {
            Ok(n) => println!("{n}"),
            Err(..) => {}
        }
    }
}