#include <iostream>
#include <string>

using namespace std;

class BigInt {
public:
  string num;
  BigInt() {
    num = "";
  }
  BigInt(string n) {
    num = n;
  }

  BigInt operator+(const BigInt & b1) const {
    return BigInt(num + b1.num);
  }
  
  bool operator<(const BigInt & b1) const{
    if(num.size() != b1.num.size()) {
      return num.size() < b1.num.size();
    }
    return num < b1.num;
  }
};


int main() {

  int h, w;
  while(cin >> w >> h && w && h) {

    BigInt table[h+1][w+1];
    
    for(int i = 0; i < h; i++) {
      string line;
      cin >> line;
      for(int j = 0; j < w; j++) {
	if('0' <= line[j] && line[j] <= '9') {
	  table[i][j].num = line[j];
	}
      }
    }
    
    for(int i = h-1; i >= 0; i--) {
      for(int j = w-1; j >= 0; j--) {
	if(table[i][j].num != "") {
	  table[i][j] = max(table[i][j] + table[i+1][j],
			     table[i][j] + table[i][j+1]);
	}
      }
    }

    BigInt ans = BigInt("");
    for(int i = 0; i < h; i++) {
      for(int j = 0; j < w; j++) {
	if(table[i][j].num != "" && 
	   !(table[i][j].num.size() >= 2 && table[i][j].num[0] == '0')) {
	  ans = max(ans, table[i][j]);
	}
      }
    }
    cout << ans.num << endl;
  }
}