use std::io::{self, Read};

type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;

fn get_input_string() -> io::Result<String> {
    let mut buffer = String::new();
    io::stdin().read_to_string(&mut buffer)?;
    Ok(buffer)
}

fn main() -> Result<()> {
    let mass_list: Vec<_> = get_input_string()?
        .split("\n")
        .filter(|n| !n.is_empty())
        .map(|n| n.parse::<u64>().unwrap())
        .collect();
    part1(&mass_list);
    part2(&mass_list);
    Ok(())
}

fn part1(mass_list: &Vec<u64>) {
    let total: u64 = mass_list.iter()
        .copied()
        .map(fuel_req)
        .sum();

    println!("Part 1: {}", total);
}

fn fuel_req(mass: u64) -> u64 {
    let frac = mass / 3;
    if frac <= 2 {
        0
    } else {
        frac - 2
    }
}

fn part2(mass_list: &Vec<u64>) {
    let total: u64 = mass_list.iter()
        .copied()
        .map(full_fuel_req)
        .sum();
    
    println!("Part 2: {}", total);
}

fn full_fuel_req(mass: u64) -> u64 {
    let req = fuel_req(mass);
    if req == 0 {
        0
    } else {
        req + full_fuel_req(req)
    }
}