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

public class Main {

	static PrintWriter out;
	static InputReader ir;

	static void solve() {
		for (;;) {
			int m = ir.nextInt();
			int n = ir.nextInt();
			if (m == 0 && n == 0)
				return;
			char[][] map = ir.nextCharMap(n, m);
			String[][] dp = new String[n][m];
			String ret = "";
			for (int i = n-1; i >= 0; i--) {
				for (int j = m-1; j >= 0; j--) {
					if (map[i][j] >= 'A' && map[i][j] <= 'Z')
						continue;
					dp[i][j] = Character.toString(map[i][j]);
					for (int k = 0; k < 2; k++) {
						int nx = i + (k & 1);
						int ny = j + ((k & 1) ^ 1);
						if (!(nx >= 0 && nx < n && ny >= 0 && ny < m))
							continue;
						if( map[nx][ny] >= 'A' && map[nx][ny] <= 'Z')
							continue;
						dp[i][j] = max(dp[i][j], Character.toString(map[i][j]) + dp[nx][ny]);
					}
					int t=0;
					while(t<dp[i][j].length()&&dp[i][j].charAt(t)=='0')
						t++;
					ret=max(ret,dp[i][j].substring(t));
				}
			}
			out.println(ret);
		}
	}

	static String max(String a, String b) {
		if (a.length() > b.length())
			return a;
		if (a.length() < b.length())
			return b;
		for (int i = 0; i < a.length(); i++) {
			if (a.charAt(i) > b.charAt(i))
				return a;
			if (a.charAt(i) < b.charAt(i))
				return b;
		}
		return a;
	}

	public static void main(String[] args) throws Exception {
		ir = new InputReader(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}

	static class InputReader {

		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;

		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}

		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}

		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}

		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}

		public boolean hasNext() {
			skip();
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		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 char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}
}



Measured memory_bytes: 61276