#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{HashMap, HashSet};

mod util {
    use std::io::stdin;
    use std::str::FromStr;
    use std::fmt::Debug;

    #[allow(dead_code)]
    pub fn line() -> String {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.trim().to_string()
    }

    #[allow(dead_code)]
    pub fn get<T: FromStr>() -> T
    where
        <T as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.trim().parse().unwrap()
    }

    #[allow(dead_code)]
    pub fn gets<T: FromStr>() -> Vec<T>
    where
        <T as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.split_whitespace()
            .map(|t| t.parse().unwrap())
            .collect()
    }

    #[allow(dead_code)]
    pub fn get2<T: FromStr, U: FromStr>() -> (T, U)
    where
        <T as FromStr>::Err: Debug,
        <U as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        let mut iter = line.split_whitespace();
        (
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
        )
    }

    #[allow(dead_code)]
    pub fn get3<S: FromStr, T: FromStr, U: FromStr>() -> (S, T, U)
    where
        <S as FromStr>::Err: Debug,
        <T as FromStr>::Err: Debug,
        <U as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        let mut iter = line.split_whitespace();
        (
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
        )
    }
}

// std::cmp::Reverse doesn't have Clone.
#[derive(Eq, PartialEq, Clone)]
struct Rev<T>(pub T);

impl<T: PartialOrd> PartialOrd for Rev<T> {
    fn partial_cmp(&self, other: &Rev<T>) -> Option<Ordering> {
        other.0.partial_cmp(&self.0)
    }
}

impl<T: Ord> Ord for Rev<T> {
    fn cmp(&self, other: &Rev<T>) -> Ordering {
        other.0.cmp(&self.0)
    }
}

#[allow(unused_macros)]
macro_rules! debug {
    ($x: expr) => {
        println!("{}: {:?}", stringify!($x), $x)
    }
}

fn dfs(
    u: &[Vec<char>],
    i: usize,
    ans: &mut Vec<(String, String)>,
    memo: &mut HashSet<String>,
) -> bool {
    if i == u.len() {
        return true;
    }

    for k in 1..3 {
        let l: String = u[i][..k].iter().cloned().collect();
        let r: String = u[i][k..].iter().cloned().collect();
        if !memo.contains(&l) && !memo.contains(&r) {
            memo.insert(l.clone());
            memo.insert(r.clone());

            ans.push((l.clone(), r.clone()));
            if dfs(u, i + 1, ans, memo) {
                return true;
            } else {
                ans.pop();
                memo.remove(&l);
                memo.remove(&r);
            }
        }

        if u[i][0] == u[i][2] {
            break;
        }
    }
    return false;
}

fn main() {
    let n: (usize) = util::get();
    let u: Vec<Vec<char>> = (0..n).map(|_| util::line().chars().collect()).collect();

    let mut ans = Vec::new();

    if dfs(&u, 0, &mut ans, &mut HashSet::new()) {
        for &(ref a, ref b) in &ans {
            println!("{} {}", a, b);
        }
    } else {
        println!("Impossible");
    }

}