using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Text;

public class Program
{
    public void Proc() {
        Reader.IsDebug = false;
        int inputCount = int.Parse(Reader.ReadLine());
        this.WordList = new string[inputCount];
        for(int i=0; i<inputCount; i++) {
            this.WordList[i] = Reader.ReadLine();
        }
        if(inputCount > ('z'-'a') + ('Z' - 'A') + 2) {
            Console.WriteLine("Impossible");
            return;
        }
        List<string> ans = this.GetAns(0, new Dictionary<string, int>());
        if(ans == null) {
            Console.WriteLine("Impossible");
        } else {
            ans.ForEach(a=>Console.WriteLine(a));
        }
    }

    private List<string> GetAns(int idx, Dictionary<string, int> dic) {
        string str1 = WordList[idx].Substring(0,1);
        string str2 = WordList[idx].Substring(1,2);
        if((!dic.ContainsKey(str1)) && (!dic.ContainsKey(str2))) {
            if(idx < this.WordList.Length - 1) {
                dic.Add(str1, idx);
                dic.Add(str2, idx);
                List<string> tmp = GetAns(idx+1, dic);
                dic.Remove(str1);
                dic.Remove(str2);
                if(tmp != null) {
                    tmp.Insert(0, str1 + " " + str2);
                    return tmp;
                }
            } else {
                return new string[] {str1 + " " + str2}.ToList();
            }
        }
        if(str1.Equals(this.WordList[idx].Substring(2)) || str2.Equals(this.WordList[idx].Substring(0,2))) {
            return null;
        }
        str1 = this.WordList[idx].Substring(0, 2);
        str2 = this.WordList[idx].Substring(2, 1);   
        if((!dic.ContainsKey(str1)) && (!dic.ContainsKey(str2))) {
            if(idx < this.WordList.Length - 1) {
                dic.Add(str1, idx);
                dic.Add(str2, idx);
                List<string> tmp = GetAns(idx+1, dic);
                dic.Remove(str1);
                dic.Remove(str2);
                if(tmp != null) {
                    tmp.Insert(0, str1 + " " + str2);
                    return tmp;
                }
            } else {
                return new string[] {str1 + " " + str2}.ToList();
            }
        }
        return null;
    }

    private string[] WordList;
    public class Reader {
        public static bool IsDebug = true;
        private static System.IO.StringReader SReader;
        private static string InitText = @"



";
        public static string ReadLine() {
            if(IsDebug) {
                if(SReader == null) {
                    SReader = new System.IO.StringReader(InitText.Trim());
                }
                return SReader.ReadLine();
            } else {
                return Console.ReadLine();
            }
        }
    }
    public static void Main(string[] args)
    {
        Program prg = new Program();
        prg.Proc();
    }
}