package no470a;

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {

	public static void main(String[] args) {
		IO io = new IO();
		int n = io.nextInt();
		String[] u = new String[n];
		for(int i=0;i<n;i++) {
			u[i] = io.next();
		}
		if (n > 60) {
			io.println("Impossible");
			io.flush();
			return;
		}
		String[][] s = new String[n][2];
		String[][] t = new String[n][2];
		for(int i=0;i<n;i++) {
			s[i][0] = u[i].substring(0, 1);
			s[i][1] = u[i].substring(0, 2);
			t[i][0] = u[i].substring(1, 3);
			t[i][1] = u[i].substring(2, 3);
		}
		
		int[] div = new int[n];
		Arrays.fill(div, -1);
		for(int i=0;i<n;i++) {
			if (div[i] != -1) continue;
			boolean success = false;
			LOOP: for(int j=0;j<2;j++) {
				int[] div2 = Arrays.copyOf(div, n);
				div2[i] = j;
				HashSet<String> hs = new HashSet<>();
				for(int k=0;k<n;k++) {
					if (div2[k] != -1) {
						hs.add(s[k][div2[k]]);
						hs.add(t[k][div2[k]]);
					}
				}
				boolean update = true;
				while(update) {
					update = false;
					for(int k=0;k<n;k++) {
						if (div2[k] != -1) continue;
						boolean leftOK = !hs.contains(s[k][0]) && !hs.contains(t[k][0]);
						boolean rightOK = !hs.contains(s[k][1]) && !hs.contains(t[k][1]);
						if (leftOK && !rightOK) {
							div2[k] = 0;
							hs.add(s[k][0]);
							hs.add(t[k][0]);
							update = true;
						}else if(!leftOK && rightOK) {
							div2[k] = 1;
							hs.add(s[k][1]);
							hs.add(t[k][1]);
							update = true;
						}else if(!leftOK && !rightOK) {
							continue LOOP;
						}
					}
				}
				div = div2;
				success = true;
				break;
			}
			if (!success) {
				io.println("Impossible");
				io.flush();
				return;
			}
		}
		for(int i=0;i<n;i++) {
			if (div[i] == 0) {
				io.println(s[i][0] + " " + t[i][0]);
			}else{
				io.println(s[i][1] + " " + t[i][1]);
			}
		}
		io.flush();
	}
}
//1. 任意の文字列を選び、分割の方法を2通り試す
//2. 分割の方法が確定するものをすべて分割する
//3. 失敗したらもう片方を試す。成功したらそれらの方法を確定。
class IO extends PrintWriter {
	private final InputStream in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	
	public IO() { this(System.in);}
	public IO(InputStream source) { super(System.out); this.in = source;}
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	private static boolean isNewLine(int c) { return c == '\n' || c == '\r';}
	public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
	public boolean hasNextLine() { while(hasNextByte() && isNewLine(buffer[ptr])) ptr++; return hasNextByte();}
	public String next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public char[] nextCharArray(int len) {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		char[] s = new char[len];
		int i = 0;
		int b = readByte();
		while(isPrintableChar(b)) {
			if (i == len) {
				throw new InputMismatchException();
			}
			s[i++] = (char) b;
			b = readByte();
		}
		return s;
	}
	public String nextLine() {
		if (!hasNextLine()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(!isNewLine(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
			throw new NumberFormatException();
		}
		return (int) nl;
	}
	public char nextChar() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		return (char) readByte();
	}
	public double nextDouble() { return Double.parseDouble(next());}
	public int[] nextIntArray(int n) { int[] a = new int[n]; for(int i=0;i<n;i++) a[i] = nextInt(); return a;}
	public long[] nextLongArray(int n) { long[] a = new long[n]; for(int i=0;i<n;i++) a[i] = nextLong(); return a;}
	public double[] nextDoubleArray(int n) { double[] a = new double[n]; for(int i=0;i<n;i++) a[i] = nextDouble(); return a;}
	public void nextIntArrays(int[]... a) { for(int i=0;i<a[0].length;i++) for(int j=0;j<a.length;j++) a[j][i] = nextInt();}
	public int[][] nextIntMatrix(int n,int m) { int[][] a = new int[n][]; for(int i=0;i<n;i++) a[i] = nextIntArray(m); return a;}
	public char[][] nextCharMap(int n,int m) { char[][] a = new char[n][]; for(int i=0;i<n;i++) a[i] = nextCharArray(m); return a;}
	public void close() { super.close(); try {in.close();} catch (IOException e) {}}
}