#include<bits/stdc++.h>
using namespace std;
#define begin int main(){
#define end return 0; }
char tmp;
char mp[4][22];
begin
	int c,r;cin>>c>>r;
	for(int i=1;i<=r;i++)
	for(int j=1;j<=c;j++){
		char a;cin>>a;
		mp[i][j]=a=='#'?tmp:a;
	}
	string mins="zzzzzzzzzzzzzzzzzzz";
	for(int i=1;i<=r;i++)
	for(int j=1;j<=c;j++){
		if(mp[i][j]){
			int lj=j;string a="";
			while(mp[i][lj++] && i<=r &&lj<=c) {
			a+=mp[i][lj];
			if(a.size()>=2 && (mp[i][j-1]=='#' || j-1==0) &&(mp[i][lj+1]=='#' || lj+1>c) ){
				mins=min(mins,a);
			}
			
			}
			int li=i;a="";
			while(mp[li++][j] && li<=r &&j<=c) {
			a+=mp[li][j];
			if(a.size()>=2)
			if(a.size()>=2 && (mp[i-1][j]=='#' || i-1==0) &&(mp[li+1][j]=='#' || li+1>r) ){
				mins=min(mins,a);
			}
			}
		}
	}
	cout<<mins;
end