using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		if(N > 52){
			Console.WriteLine("Impossible");
			return;
		}
		
		HashSet<String> one = new HashSet<String>();
		HashSet<String> two = new HashSet<String>();
		for(int i=0;i<N;i++){
			one.Add(S[i].Substring(0,1));
			one.Add(S[i].Substring(2));
			two.Add(S[i].Substring(0,2));
			two.Add(S[i].Substring(1));
		}
		if(one.Count<N || two.Count<N){
			Console.WriteLine("Impossible");
			return;
		}
		
		
		
		String[] S0 = new String[N];
		for(int i=0;i<N;i++)S0[i] = S[i];
		
		int[] ord = Enumerable.Range(0,N).ToArray();
		Array.Sort(S,ord);
		
		h = new HashSet<String>();
		found = false;
		route = new int[N];
		dfs(0);
		
		if(!found){
			Console.WriteLine("Impossible");
			return;
		}
		
		Array.Sort(ord,ans);
		for(int i=0;i<N;i++){
			Console.WriteLine("{0} {1}",S0[i].Substring(0,ans[i]),S0[i].Substring(ans[i]));
		}
		
		
		
	}
	
	Stopwatch sw;
	
	bool found;
	int[] route;
	int[] ans;
	HashSet<String> h;
	void dfs(int now){
		if(found) return;
		if(sw.ElapsedMilliseconds >= 1800) return;
		if(now == N){
			found = true;
			ans = new int[N];
			for(int i=0;i<N;i++) ans[i] = route[i];
			return;
		}
		for(int j=1;j<=2;j++){
			var s0 = S[now].Substring(0,j);
			var s1 = S[now].Substring(j);
			if(!h.Contains(s0) && !h.Contains(s1)){
				h.Add(s0);
				h.Add(s1);
				route[now] = j;
				dfs(now+1);
				route[now] = 0;
				h.Remove(s0);
				h.Remove(s1);
			}
		}
	}
	
	
	
	int N;
	String[] S;
	public Sol(){
		sw = new Stopwatch();
		sw.Start();
		
		N = ri();
		S = new String[N];
		for(int i=0;i<N;i++) S[i] = rs();
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}