use std::collections::HashMap;
use std::str::FromStr;

pub fn run(input: &str) {
    let mut first = Vec::<i64>::new();
    let mut second = Vec::<i64>::new();
    for line in input.split('\n') {
        if let Some((first_part, second_part)) = line.split_once("   ") {
            match i64::from_str(first_part) {
                Ok(n) => first.push(n),
                Err(err) => {
                    eprintln!("Failed to parse first number from {}: {}", first_part, err);
                }
            }
            match i64::from_str(second_part) {
                Ok(n) => second.push(n),
                Err(err) => {
                    eprintln!("Failed to parse second number from {}: {}", second_part, err);
                }
            }
        }
    }

    let mut second_counts = HashMap::<i64, i64>::new();
    for element in second {
        *second_counts.entry(element).or_insert(0) += 1;
    }
    
    let result = first.iter().map(|num| num * second_counts.get(num).unwrap_or(&0)).sum::<i64>();
    println!("Similarity: {}", result);
}