#include <iostream>
using namespace std;
int main(){
	int a,b;
	cin>>a>>b;
	do{
		for(int i=1;i<=a;i++){
			for(int j=1;j<=b;j++){
				if ((i+j)%2==0)
					cout<<"#";
				else cout<<".";
				}
			cout<<endl;
			}
			cin>>a>>b;
			cout<<endl;
		}while (a!=0 || b!=0);
}
