#include<iostream>
using namespace std;
int main (){
	int j,k,H,W;
	while(1){
		cin>>H>>W;

		for(j=1;j<=H;j++){

			for(k=1;k<=W;k++){

				if((j+k)%2==0){
					cout<<"#";
				}
				else{
					cout<<".";
				}
			}
			cout<<endl;



		}    if(H==0&&W==0){
			break;
		}cout<<endl;
	}
	return 0;
}
