use std::io::{stdin, BufRead};
use anyhow::{anyhow, Result};

fn collect_list(prefix: &str, buf: &str) -> Result<Vec<usize>> {
    Ok(buf.strip_prefix(prefix)
    .ok_or(anyhow!("Incorrect line: {buf:?}"))?
    .split_whitespace()
    .map(|v| v.parse::<usize>())
    .collect::<Result<_,_>>()?)
}

fn aggregate(nums: &[usize]) -> usize {
    nums.iter().fold(0, |acc, d| { acc * (10u64.pow(d.ilog10() + 1) as usize) + d } )
}

fn ways((t,d) : (usize, usize)) -> usize {
    if t*t < 4*d { return 0; }
    let dq = t*t - 4*d;

    let delta = (dq as f64).sqrt();
    let b1 = ((t as f64 - delta)/2f64).floor() as usize + 1;
    let b2 = ((t as f64 + delta)/2f64).ceil() as usize - 1;

    if b2 < b1 { return 0; }

    eprintln!("t={t} d={d} b1={b1} b2={b2}");

    b2 - b1 + 1
}

fn main() -> Result<()> {
    let mut stdin = stdin().lock();

    let mut buf = String::with_capacity(1024);

    stdin.read_line(&mut buf)?;
    let times = collect_list("Time:", &buf)?;
    buf.clear();

    stdin.read_line(&mut buf)?;
    let distances = collect_list("Distance:", &buf)?;
    buf.clear();


    let ways1: usize = times.iter().copied()
        .zip(distances.iter().copied())
        .map(ways)
        .product();

    println!("Part 1: {ways1} ways.");

    let time2 = aggregate(&times);
    let dist2 = aggregate(&distances);

    let ways2 = ways((time2, dist2));

    println!("Part 2: {ways2} ways.");

    Ok(())
}