fn count_digits(n:i32)->i32 { if n==0 {1} else {n.ilog10() as i32+1} }
use std::sync::mpsc::{self, Receiver, Sender};
struct Job { n: i32 }
struct Result { n: i32, digits: i32 }
fn worker(jobs: Receiver<Job>, results: Sender<Result>) {
    for job in jobs {
        if job.n < 0 { break; }
        results.send(Result { n: job.n, digits: count_digits(job.n) }).unwrap();
    }
}
fn main() {
    let n=std::thread::available_parallelism().map_or(1,usize::from);
    let (results_tx,results_rx)=mpsc::channel();
    let mut jobs=Vec::new();let mut ids=Vec::new();
    for _ in 0..n {
        let (tx,rx)=mpsc::channel(); let results=results_tx.clone();
        jobs.push(tx);ids.push(std::thread::spawn(move || worker(rx,results)));
    }
    for i in 0..8 { jobs[i % n].send(Job {n:1 << (i*3)}).unwrap(); }
    for queue in &jobs { queue.send(Job {n:-1}).unwrap(); }
    let mut total=0;
    for _ in 0..8 { let r=results_rx.recv().unwrap();total+=r.digits; }
    for id in ids { id.join().unwrap(); }
    println!("{n} workers, {total} digits in total");
}