typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    ll h,w;
    std::cin >> h>>w;
    vector<vector<pair<ll,ll>>> prev(h,vector<pair<ll,ll>>(w,{-1,-1}));
    vector<string> s(h);
    for (int i = 0; i < h; i++) {
        std::cin >> s[i];
    }
    priority_queue<tuple<ll,ll,ll>,vector<tuple<ll,ll,ll>>,greater<tuple<ll,ll,ll>>> pq;
    if(s[0][1]>s[1][0]){
        pq.push({1, s[1][0],1});
        prev[1][0] = {0,0};
    }else if(s[1][0]>s[0][1]){
        pq.push({1, s[0][1],0});
        prev[0][1] = {0,0};
    }else{
        pq.push({1, s[1][0],1});
        pq.push({1, s[1][0],1});
        prev[0][1] = {0,0};
        prev[1][0] = {0,0};
    }
    vector<ll> minc(h+w+2,1000);
    
    while(!pq.empty()){
        auto [now, ch, y] = pq.top();pq.pop();
        // std::cout << now<<" "<<ch << std::endl;
        if(minc[now]<ch)continue;
        minc[now] = ch;
        auto x = now-y;
        // std::cout << now<<" "<<x<<" "<<y << std::endl;
        if(x==w-1&&y==h-1)break;
        if(x==w-1){
            pq.push({now+1, s[y+1][x] ,y+1});
            prev[y+1][x] = {y, x};
        }else if(y==h-1){
            pq.push({now+1, s[y][x+1],y});
            prev[y][x+1] = {y,x};
        }else{
            pq.push({now+1, s[y+1][x] ,y+1});
            prev[y+1][x] = {y, x};
            pq.push({now+1, s[y][x+1],y});
            prev[y][x+1] = {y,x};
        }
    }
    string ans = "";
    pair<ll,ll> now = {h-1,w-1};
    while(true){
        ans += s[now.first][now.second];
        if(now.first==0&&now.second==0)break;
        now = prev[now.first][now.second];
    }
    reverse(ans.begin(),ans.end());
    std::cout << ans << std::endl;
}