package adv2016; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class N470_2 { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(); char[][] u = new char[n][]; for(int i = 0;i < n;i++){ u[i] = ns(3); } if(n > 52){ out.println("Impossible"); return; } int[] from = new int[n*n*4]; int[] to = new int[n*n*4]; int p = 0; for(int i = 0;i < n;i++){ for(int j = i+1;j < n;j++){ for(int k = 0;k < 2;k++){ for(int l = 0;l < 2;l++){ int indk = k == 0 ? 0 : 2; int indl = l == 0 ? 0 : 2; int iind = k == 0 ? i : i+n; int iindi = 2*i+n-iind; int jind = l == 0 ? j : j+n; int jindi = 2*j+n-jind; int xk = k == 0 ? 1 : 0; int xl = l == 0 ? 1 : 0; if(u[i][indk] == u[j][indl] || u[i][xk] == u[j][xl] && u[i][xk+1] == u[j][xl+1]){ from[p] = iind; to[p] = jindi; p++; from[p] = jind; to[p] = iindi; p++; } } } } } int[][] g = packD(2*n, from, to, p); int[] sign = restore2SAT(g); if(sign == null){ out.println("Impossible"); return; } for(int i = 0;i < n;i++){ if(sign[i] == 1){ out.println(u[i][0] + " " + u[i][1] + u[i][2]); }else{ out.println("" + u[i][0] + u[i][1] + " " + u[i][2]); } } } public static int[] restore2SAT(int[][] g) { assert g.length % 2 == 0; int n = g.length/2; int[] clus = decomposeToSCC(g); int[] ret = new int[n]; for(int i = 0;i < n;i++){ if(clus[i] == clus[i+n])return null; // unsatisfied ret[i] = clus[i] > clus[i+n] ? -1 : 1; } return ret; } public static int[] decomposeToSCC(int[][] g) { int n = g.length; int[] stack = new int[n+1]; int[] ind = new int[n+1]; int[] ord = new int[n]; Arrays.fill(ord, -1); int[] low = new int[n]; Arrays.fill(low, -1); int sp = 0; int id = 0; // preorder int[] clus = new int[n]; int cid = 0; int[] cstack = new int[n+1]; int csp = 0; boolean[] incstack = new boolean[n]; for(int i = 0;i < n;i++){ if(ord[i] == -1){ ind[sp] = 0; cstack[csp++] = i; stack[sp++] = i; incstack[i] = true; while(sp > 0){ int cur = stack[sp-1]; if(ind[sp-1] == 0){ ord[cur] = low[cur] = id++; } if(ind[sp-1] < g[cur].length){ int nex = g[cur][ind[sp-1]]; if(ord[nex] == -1){ ind[sp-1]++; ind[sp] = 0; incstack[nex] = true; cstack[csp++] = nex; stack[sp++] = nex; }else{ // shortcut // U.tr(cur, nex, incstack[nex], low[nex], stack); if(incstack[nex])low[cur] = Math.min(low[cur], low[nex]); ind[sp-1]++; } }else{ if(ord[cur] == low[cur]){ while(csp > 0){ incstack[cstack[csp-1]] = false; clus[cstack[--csp]] = cid; if(cstack[csp] == cur)break; } cid++; } if(--sp >= 1)low[stack[sp-1]] = Math.min(low[stack[sp-1]], low[stack[sp]]); } } } } return clus; } public static int[][] packD(int n, int[] from, int[] to){ return packD(n, from, to, from.length);} public static int[][] packD(int n, int[] from, int[] to, int sup) { int[][] g = new int[n][]; int[] p = new int[n]; for(int i = 0;i < sup;i++)p[from[i]]++; for(int i = 0;i < n;i++)g[i] = new int[p[i]]; for(int i = 0;i < sup;i++){ g[from[i]][--p[from[i]]] = to[i]; } return g; } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new N470_2().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }