import java.util.*; import java.io.*; import java.math.*; public class Main{ //見なくていいよ ここから------------------------------------------ static class InputIterator{ ArrayList inputLine = new ArrayList<>(1024); int index = 0; int max; String read; InputIterator(){ try{ BufferedReader br = new BufferedReader(new InputStreamReader(System.in, "UTF-8")); while((read = br.readLine()) != null){ inputLine.addAll(Arrays.asList(read.split(" "))); } }catch(IOException e){} max = inputLine.size(); } boolean hasNext(){return (index < max);} String next(){ if(hasNext()){ return inputLine.get(index++); }else{ throw new IndexOutOfBoundsException("There is no more input"); } } } static HashMap CONVSTR = new HashMap<>(); static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem. static PrintWriter out = new PrintWriter(System.out); static void flush(){out.flush();} static void myout(Object t){out.println(t);} static void myerr(Object... t){System.err.print("debug:");System.err.println(Arrays.deepToString(t));} static String next(){return ii.next();} static boolean hasNext(){return ii.hasNext();} static int nextInt(){return Integer.parseInt(next());} static long nextLong(){return Long.parseLong(next());} static double nextDouble(){return Double.parseDouble(next());} static ArrayList nextCharArray(){return myconv(next(), 0);} static ArrayList nextStrArray(int size){ ArrayList ret = new ArrayList<>(size); for(int i = 0; i < size; i++){ ret.add(next()); } return ret; } static ArrayList nextIntArray(int size){ ArrayList ret = new ArrayList<>(size); for(int i = 0; i < size; i++){ ret.add(Integer.parseInt(next())); } return ret; } static ArrayList nextLongArray(int size){ ArrayList ret = new ArrayList<>(size); for(int i = 0; i < size; i++){ ret.add(Long.parseLong(next())); } return ret; } @SuppressWarnings("unchecked") static String myconv(Object list, int no){//only join StringBuilder sb = new StringBuilder(""); String joinString = CONVSTR.get(no); if(list instanceof String[]){ return String.join(joinString, (String[])list); }else if(list instanceof long[]){ long[] tmp = (long[])list; if(tmp.length == 0){ return ""; } sb.append(String.valueOf(tmp[0])); for(int i = 1; i < tmp.length; i++){ sb.append(joinString).append(String.valueOf(tmp[i])); } return sb.toString(); }else if(list instanceof int[]){ int[] tmp = (int[])list; if(tmp.length == 0){ return ""; } sb.append(String.valueOf(tmp[0])); for(int i = 1; i < tmp.length; i++){ sb.append(joinString).append(String.valueOf(tmp[i])); } return sb.toString(); }else if(list instanceof ArrayList){ ArrayList tmp = (ArrayList)list; if(tmp.size() == 0){ return ""; } sb.append(tmp.get(0)); for(int i = 1; i < tmp.size(); i++){ sb.append(joinString).append(tmp.get(i)); } return sb.toString(); }else{ throw new ClassCastException("Don't join"); } } static ArrayList myconv(String str, int no){//only split String splitString = CONVSTR.get(no); return new ArrayList(Arrays.asList(str.split(splitString))); } static ArrayList myconv(String str, String no){ return new ArrayList(Arrays.asList(str.split(no))); } public static void main(String[] args){ CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, ""); solve();flush(); } //見なくていいよ ここまで------------------------------------------ //このコードをコンパイルするときは、「-encoding UTF-8」を指定すること static void solve(){//ここがメイン関数 int H = nextInt(); int W = nextInt(); Node[][] list = new Node[H][W]; for(int i = 0; i < H; i++){ String s = next(); for(int j = 0; j < W; j++){ String c = s.substring(j, j + 1); list[i][j] = new Node(i, j, c); } } ArrayDeque queue = new ArrayDeque<>(); queue.add(new Edge(0, 0)); list[0][0].access = true; while(queue.size() > 0){ ArrayList nx = new ArrayList<>(); while(queue.size() > 0){ Edge tmp = queue.pollFirst(); int y = tmp.y; int x = tmp.x; if(y < H - 1){ nx.add(list[y + 1][x]); } if(x < W - 1){ nx.add(list[y][x + 1]); } } if(nx.size() == 0){ break; } Collections.sort(nx); String ok = nx.get(0).S; for(Node nxn : nx){ if(nxn.S.equals(ok) && !nxn.access){ nxn.access = true; list[nxn.y][nxn.x].access = true; queue.add(new Edge(nxn.y, nxn.x)); } } } int lastY = H - 1; int lastX = W - 1; String[] output = new String[H + W - 1]; int lastIndex = H + W - 2; while(true){ output[lastIndex] = list[lastY][lastX].S; lastIndex--; if(lastY == 0 && lastX == 0){ break; } if(lastY > 0 && lastX > 0){ if(list[lastY - 1][lastX].access){ lastY--; }else{ lastX--; } }else if(lastY > 0){ lastY--; }else{ lastX--; } } myout(myconv(output, 0)); } //メソッド追加エリア ここから static class Node implements Comparable{ String S; int y; int x; boolean access = false; Node(int y, int x, String S){ this.S = S; this.y = y; this.x = x; } public int compareTo(Node ato){ return this.S.compareTo(ato.S); } } static class Edge{ int y; int x; Edge(int y, int x){ this.x = x; this.y = y; } } //メソッド追加エリア ここまで }