/*
 * GCA : "Computer is artificial subject absolutely,Math is God"
 */
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
#include <ctime>
using namespace std;
#ifdef DEBUG
#define VAR(a,b) __typeof(b) a=(b)
#define debug(...) printf("DEBUG: "),printf(__VA_ARGS__)
#else
#define VAR(a,b) __typeof(b) a=(b)
#define debug(...)
#endif
typedef unsigned int uint;
typedef long long int Int;
typedef unsigned long long int UInt;
#define Set(a,s) memset(a,s,sizeof(a))
#define Pln() printf("\n")
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define M 25
#define PB push_back
#define oo INT_MAX
#define FOR(a,b) for(VAR(a,(b).begin());a!=(b).end();++a)
#define eps 1e-9
#define X first
#define Y second
inline bool xdy(double x,double y){return x>y+eps;}
inline bool xddy(double x,double y){return x>y-eps;}
inline bool xcy(double x,double y){return x<y-eps;}
inline bool xcdy(double x,double y){return x<y+eps;}
const Int mod=1000000007;
int nx,ny;
char mz[M][M];
set<string> sid;
int dx[8]={0,1,1,1,0,-1,-1,-1};
int dy[8]={1,1,0,-1,-1,-1,0,1};
char store[M*M];
int ox,oy;
string ans;
bool vis[M][M];
void dfs(int x,int y,int d,int dep){

	store[dep]=mz[y][x];
	int nex=(x+dx[d]+nx)%nx;
	int ney=(y+dy[d]+ny)%ny;
	store[dep+1]=0;
	string ss(store);
	if(sid.count(ss)&&ss.length()>=2){
		if(ss.length()>ans.length())ans=ss;
		else if(ss.length()==ans.length()&&ss<ans){
			ans=ss;
		}
	}
	sid.insert(ss);
	vis[x][y]=1;
	if(!vis[nex][ney])dfs(nex,ney,d,dep+1);
	vis[x][y]=0;

}
void solve(){
	Set(vis,0);
	for(int i=0;i<ny;i++){
		for(int j=0;j<nx;j++){
			for(int k=0;k<8;k++){
				vis[j][i]=1;
				dfs(j,i,k,0);
				vis[j][i]=0;
			}
		}
	}
	if(ans.size())
		puts(ans.c_str());
	else puts("0");
}
int main() {
	ios_base::sync_with_stdio(0);
	while(~scanf("%d%d",&ny,&nx)&&ny&&nx){
		sid.clear();
		ans="";
		for(int i=0;i<ny;i++)scanf("%s",mz[i]);
		solve();

	}

















}