#ifdef LOCAL
    #define _GLIBCXX_DEBUG
    #define __clock__
#else
    #pragma GCC optimize("Ofast")
#endif
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;
using PII = pair<ll, ll>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\n'; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<'\n'
#define p2(s, t) cout << (s) << " " << (t) << '\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\n'
#define p_yes() p("YES")
#define p_no() p("NO")
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())
#define MP make_pair

ll SUM(VI& V){
  return accumulate(ALL(V), 0LL);
}

void print_vector(VI& V){
  ll n = V.size();
  rep(i, n){
    if(i) cout << ' ';
    cout << V[i];
  }
  cout << endl;
}

ll gcd(ll a,ll b){
    if(b == 0) return a;
    return gcd(b,a%b);
}

ll lcm(ll a,ll b){
    ll g = gcd(a,b);
    return a / g * b;
}

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);

bool ischar(char c){
  if('0'<=c && c<='9'){
    return true;
  }else{
    return false;
  }
}

string strip_zero(string s){
  ll L = s.size();
  if(L==0) return "";
  rep(i,L){
    char c = s[i];
    if(c!='0'){
      return s.substr(i);
    }
  }
  return "0";
}

// 文字列を数字にしたときの大小比較
string str_max(string a, string b){
  string c = strip_zero(a);
  string d = strip_zero(b);
  if(c.size()<d.size()){
    // return d;
    return b;
  }else if(c.size()>d.size()){
    // return c;
    return a;
  }else{
    ll L = c.size();
    rep(i,L){
      if(c[i]>d[i]){
        // return c;
        return a;
      }else if(c[i]<d[i]){
        // return d;
        return b;
      }
    }
  }
  // return c;
  return a;
}

ll W,H;
VS S;

string dp[80][80];
void reset(){
  rep(i,80)rep(j,80)dp[i][j]="";
}

// そこから作れる最大の文字列
// 00001234など
string rec(ll i, ll j){
  if(dp[i][j]!="") return dp[i][j];
  
  bool can_right=false;
  if(j+1<=W-1 && ischar(S[i][j+1])){
    can_right = true;
  }

  bool can_lower=false;
  if(i+1<=H-1 && ischar(S[i+1][j])){
    can_lower = true;
  }

  string ret;
  if(!can_right && !can_lower){
    string a{S[i][j]};
    ret = a;
  }else if(!can_right && can_lower){
    // 下にだけ行ける
    ret = S[i][j] + rec(i+1, j);
  }
  else if(can_right && !can_lower){
    // 右にだけ行ける
    ret = S[i][j] + rec(i, j+1);
  }
  else{
    // 右にも下にも行ける
    string a = S[i][j] + rec(i, j+1);
    string b = S[i][j] + rec(i+1, j);
    ret = str_max(a,b); // ?
  }
  return dp[i][j] = ret;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    while(cin>>W>>H){
      if(W==0) return 0;
      S.resize(H);
      rep(i,H){
        cin>>S[i];
      }

      reset();

      string ma = "";
      rep(i,H){
        rep(j,W){
          char c = S[i][j];
          if(ischar(c) && c!='0'){
            string s = rec(i,j);
            ma = str_max(ma, s);
          }
        }
      }
      p(ma);
    }
    return 0;
}


Measured memory_bytes: 3420