import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class PrintCheckboatd {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        StringTokenizer st=new StringTokenizer(br.readLine());
        int H=Integer.parseInt(st.nextToken());
        int W=Integer.parseInt(st.nextToken());

        while(H!=0 || W!=0) {

            int i=0;
            int j=0;

            while(j<H) {
                if(j%2==1){
                	while(i<W) {
                        if(i%2==1){
                        	System.out.print("#");
                        }else{
                        	System.out.print(".");
                        }
                        i++;
                    }
                }else{
                	while(i<W) {
                        if(i%2==1){
                        	System.out.print(".");
                        }else{
                        	System.out.print("#");
                        }
                        i++;
                    }
                }
                System.out.println("");
                i=0;
                j++;
            }
            System.out.println("");
            StringTokenizer sa=new StringTokenizer(br.readLine());
            H=Integer.parseInt(sa.nextToken());
            W=Integer.parseInt(sa.nextToken());
        }
	}

}

