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

fn main() -> io::Result<()> {
    let mut l1: Vec<u64> = vec!();
    let mut l2: HashMap<u64, u64> = HashMap::default();
    for line in io::stdin().lines() {
        let line = line?;
        let parts: Vec<&str> = line.trim().split_whitespace().collect();
        let (n1, n2) = (parts[0], parts[1]);
        l1.push(n1.parse().unwrap());
        let v = l2.entry(n2.parse::<u64>().unwrap()).or_insert(0);
        *v += 1;
    }
    let mut sum = 0;
    for n1 in l1.into_iter() {
        sum += n1*l2.get(&n1).unwrap_or(&0);
    }
    println!("{}", sum);
    Ok(())
}