import java.util.*;
public class Main {
    public static void main(String[] args) {
    	Scanner sc=new Scanner(System.in);
    	while(true) {
    		int H=sc.nextInt();
    		int W=sc.nextInt();
    		if(W==0&&H==0)break;
    		for(int i=0;i<H;i++) {
    			for(int j=0;j<W;j++) {
    				if((i+j)%2==0) System.out.printf("#");
    				else System.out.printf(".");
    			}
    			System.out.printf("\n");
    		}
    		System.out.printf("\n");
    	}
        sc.close();
    }
}

