#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define each(itr,v) for(auto itr:v)
#define pb(s) push_back(s)
#define mp(a,b) make_pair(a,b)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define maxch(x,y) x=max(x,y)
#define minch(x,y) x=min(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt(x) bitset<32>(x).count()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> PPI;
typedef pair<ll, ll> PL;
typedef pair<P, ll> PPL;

#define INF INT_MAX/3

#define MAX_N 1000

int h,w;
string s[11];

int dx[]={-1,0,1,-1,1,-1,0,1};
int dy[]={-1,-1,-1,0,0,1,1,1};

int main(){
	cin.sync_with_stdio(false);
	while(1){
		cin>>h>>w;
		if(h==0)break;
		rep(i,h)cin>>s[i];
		string res="";
		map<string,int> smap;
		rep(i,h)rep(j,w){
			rep(d,8){
				string ss;
				ss+=s[i][j];
				int ny=i+dy[d],nx=j+dx[d];
				if(ny>=h)ny=0;
				if(ny<0)ny=h-1;
				if(nx>=w)nx=0;
				if(nx<0)nx=w-1;
				while(ny!=i||nx!=j){
					ss+=s[ny][nx];
					smap[ss]++;
					if(smap[ss]==2){
						if(ss.length()>res.length()||(ss.length()==res.length()&&ss<res)){
							res=ss;
						}
					}
					ny+=dy[d],nx+=dx[d];
					if(ny>=h)ny=0;
					if(ny<0)ny=h-1;
					if(nx>=w)nx=0;
					if(nx<0)nx=w-1;
				}
			}
		}
		if(res=="")cout<<0<<endl;
		else cout<<res<<endl;
	}
	return 0;
}