#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main(){
    int h, w; cin >> h >> w;
    vector<string> s(h);
    for(auto &it: s) cin >> it;

    vector<vector<string>> dp(h, vector<string>(w, "{}"));
    dp[h-1][w-1] = s[h-1][w-1];
    for(int i = h-1; i >= 0; i--){
        for(int j = w-1; j >= 0; j--){
            if(i+1 < h) dp[i][j] = min(dp[i][j], s[i][j]+dp[i+1][j]);
            if(j+1 < w) dp[i][j] = min(dp[i][j], s[i][j]+dp[i][j+1]);
        }
    }
    cout << dp[0][0] << endl;
    return 0;
}