import java.util.Scanner;

public class Main{
    public static void main(String args[]){
	Scanner sc= new Scanner(System.in);
	
	int i,j;

	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+j)%2==0){
		    System.out.print("#");
		}else{
		    System.out.print(".");
		}
	    }
	    System.out.print("\n");
	}
	}
	System.out.print("\n");
    }
}