#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=(int)2000;
const int MOD=1e9+9;
const int base=9973;
char c[N+2][N+2];
int numrow,numcol;
int length,need_row;
void build_board(){
for(int i=1;i<=numrow;++i){
for(int j=numcol+1;j<=2*numcol;++j) {
c[i][j]=c[i][j-numcol];
}
}
for(int i=numrow+1;i<=2*numrow;++i){
for(int j=1;j<=numcol;++j) {
c[i][j]=c[i-numrow][j];
}
}
for(int i=numrow+1;i<=2*numrow;++i){
for(int j=numcol+1;j<=2*numcol;++j){
c[i][j]=c[i-numrow][j-numcol];
}
}
return;
}
int p[N+2];
int cot[2][N+2][N+2];
int Get(int t,int id,int l,int r){
return ((LL)cot[t][id][r]-(LL)cot[t][id][l-1]*p[r-l+1]+(LL)MOD*MOD)%MOD;
}
//... COMPARE THE FUNCTION
int cmp_cot(pair<int,int>a,pair<int,int>b){
int low=1,high=need_row,p=0;
while (low<=high){
int mid=(low+high)/2;
if (Get(1,a.second,a.first,a.first+mid-1)==Get(1,b.second,b.first,b.first+mid-1)){
p=mid;
low=mid+1;
}
else high=mid-1;
}
return p;
}
bool compares(pair<int,int>a,pair<int,int>b){
int r=cmp_cot(a,b);
if (r==need_row) return false;
int low=1,high=length,p=0;
while (low<=high){
int mid=(low+high)/2;
if (Get(0,a.first+r,a.second,a.second+mid-1)==Get(0,b.first+r,b.second,b.second+mid-1)){
p=mid;
low=mid+1;
}
else high=mid-1;
}
if (p==length) return false;
return c[a.first+r][a.second+p]>c[b.first+r][b.second+p];
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0) ; cout.tie(0);
#define task "main"
if (fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin>>numrow>>numcol;
for(int i=1;i<=numrow;++i){
for(int j=1;j<=numcol;++j){
cin>>c[i][j];
}
}
build_board();
numrow=2*numrow;
numcol=2*numcol;
length=numcol/2;
need_row=numrow/2;
p[0]=1;
for(int i=1;i<=N;++i) p[i]=(LL)p[i-1]*base%MOD;
for(int i=1;i<=numrow;++i) {
for(int j=1;j<=numcol;++j){
cot[0][i][j]=((LL)cot[0][i][j-1]*base+c[i][j]-'a'+1)%MOD;
}
}
for(int j=1;j<=length;++j){
for(int i=1;i<=numrow;++i){
int x=Get(0,i,j,j+length-1);
cot[1][j][i]=((LL)cot[1][j][i-1]*base+x)%MOD;
}
}
pair<int,int>final={1,1};
for(int i=1;i<=need_row;++i){
for(int j=1;j<=length;++j){
if (compares(final,{i,j})) final={i,j};
}
}
for(int i=final.first;i<=final.first+need_row-1;++i){
for(int j=final.second;j<=final.second+length-1;++j){
cout<<c[i][j];
}
cout<<'\n';
}
}
