#include<iostream>
using namespace std;

int main(){
	int i, j, h, w;
	
	while(1){
		if ( h == 0 && w == 0 ) break;
		
		for( i = 0; i < h; i++ ){
			for ( j = 0; j < w; j++ ){
				if ( i + j % 2 == 0 || ( i == 0 && j == 0 )) 
					cout << "#";
				else 
					cout << ".":
			}
			cout << endl;
		}
		cout << endl;
	}
}