import java.io.PrintWriter;
import java.util.Scanner;

class Main{
    private static final Scanner sc = new Scanner(System.in);
    private static final PrintWriter out = new PrintWriter(System.out);
    public static void main(String[] Args){
        while(true){
            final int h = Integer.parseInt(sc.next());
            final int w = Integer.parseInt(sc.next());
            if(h==0&&w==0) break;
            for(int i = 0; i<h; i++){
                for(int j = 0; j<w; j++){
                    if( ( (i+j)&1)==0) out.print("#");
                    else out.print('.');
                }
                out.println();
            }
            out.println();
        }
        out.flush();
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz