import java.io.*;
public class Main {
    public static void main(String[] args) throws IOException{
        BufferedReader buf=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sbu=new StringBuilder();
        
        while(true){
            String[] num=buf.readLine().split(" ");
            int h=Integer.parseInt(num[0]);
            int w=Integer.parseInt(num[1]);
            
            if(h==0 && w==0)break;
            
            for(int i=0; i<h; i++){
                for(int j=0; j<w; j++){
                    if((i+j)%2==0)
                        sbu.append("#");
                    else
                        sbu.append(".");
                }
                sbu.append("\n");
            }
            sbu.append("\n");
        }
        System.out.print(sbu);
    }
}
/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