use std::io;
use std::io::BufRead;
use std::collections::HashMap;

fn close_enough(a: &str, b: &str) -> bool {
    let mut num = 0;

    for (ch1, ch2) in a.chars().zip(b.chars()) {
        if ch1 != ch2 {
            num += 1;
            if num > 1 { return false; }
        }
    }

    return num == 1;
}

pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
    let lines: Vec<String> = reader.lines().map(|l| l.unwrap()).collect();

    let mut num2: i64 = 0;
    let mut num3: i64 = 0;

    for line in &lines {
        let mut hist = HashMap::new();

        for ch in line.chars() {
            let value: i64 = *hist.get(&ch).unwrap_or(&0) + 1;
            hist.insert(ch, value);
        }

        let mut have2 = false;
        let mut have3 = false;
        for &num in hist.values() {
            if num == 2 { have2 = true; }
            if num == 3 { have3 = true; }
        }

        num2 += have2 as i64;
        num3 += have3 as i64;
    }

    let part1 = num2 * num3;

    // TODO: Can this be faster than n^2?
    for line1 in &lines {
        for line2 in &lines {
            if !close_enough(&line1, &line2) { continue; }

            let mut ans = String::new();

            for (ch1, ch2) in line1.chars().zip(line2.chars()) {
                if ch1 == ch2 {
                    ans.push(ch1);
                }
            }

            return Ok((part1.to_string(), ans));
        }
    }

    Err(io::Error::new(io::ErrorKind::Other, "Invalid input"))
}