import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        int i,j;
        Scanner sc = new Scanner(System.in);
        while(true){
            int H = sc.nextInt();
            int W = sc.nextInt();
            if(H==0 && W==0){
                break;
            }
                for(i=0;i<H;i++){
                    for(j=0;j<W;j++){
                        if(i%2==1 && j%2==1){
                            System.out.print("#");
                        }
                        if(i%2==0 && j%2==1){
                            System.out.print(".");                            
                        }
                        if(i%2==1 && j%2==0){
                            System.out.print(".");  
                        }
                        if(i%2==0 && j%2==0){
                            System.out.print("#");                            
                        }
                    }
                 System.out.println();                       
                }
        }
            System.out.println();
    }
}
