/*!
  @file c.cc
  @brief Solves "The Secret Number" ( http://www.u-aizu.ac.jp/conference/ACM/results/C.html )
  @author Yuta Kitamura
  @date 2005-04-09
*/

// start 18:15
// end 18:56

#include <iostream>
#include <string>

using std::cout;
using std::cin;
using std::endl;
using std::string;

typedef unsigned int uint;

bool num_less(const string& s1, const string& s2)
{
  if (s1.length() != s2.length())
    return s1.length() < s2.length();
  else
    return s1 < s2;
}

void remove_leading_zeros(string& s)
{
  if (!s.empty()) {
    string::size_type pos = s.find_first_not_of('0');
    if (pos < s.length())
      s = s.substr(s.find_first_not_of('0'));
    else
      s = "";
  }

  return;
}

string calc_secret_number(string** table, const char* const* matrix,
			  uint x, uint y, uint w, uint h)
{
  if (!table[y][x].empty())
    return table[y][x];

  string ans;

  if ('0' <= matrix[y][x] && matrix[y][x] <= '9') {
    string r =
      (x + 1 < w) ? calc_secret_number(table, matrix, x+1, y, w, h) : "";

    string d =
      (y + 1 < h) ? calc_secret_number(table, matrix, x, y+1, w, h) : "";

    if (num_less(r, d))
      ans = string(1, matrix[y][x]) + d;
    else
      ans = string(1, matrix[y][x]) + r;
  }

  table[y][x] = ans;
  return ans;
}

int main()
{
  while (cin) {
    uint w, h;
    cin >> w >> h;

    if (w == 0 && h == 0) break;

    char** matrix = new char*[h];
    string** table = new string*[h];
    for (uint i = 0; i < h; ++i) {
      matrix[i] = new char[w];
      table[i] = new string[w];
    }

    for (uint y = 0; y < h; ++y)
      for (uint x = 0; x < w; ++x)
	cin >> matrix[y][x];

    for (uint y = 0; y < h; ++y)
      for (uint x = 0; x < w; ++x)
	calc_secret_number(table, matrix, x, y, w, h);

    for (uint y = 0; y < h; ++y)
      for (uint x = 0; x < w; ++x)
	remove_leading_zeros(table[y][x]);

    string max;
    for (uint y = 0; y < h; ++y)
      for (uint x = 0; x < w; ++x)
	if (num_less(max, table[y][x]))
	  max = table[y][x];

    cout << max << endl;

    for (uint i = 0; i < h; ++i) {
      delete[] matrix[i];
      delete[] table[i];
    }
    delete[] matrix;
    delete[] table;
  }

  return 0;
}