import java.util.Scanner;

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

        while(true){
            int H =sc.nextInt();
            int W =sc.nextInt();
            if(H==0 && W==0){
                break;
            }
            for(int i=0;i<H;i++){
                for(int j=0;j<W;j++){
                    if( (i+j) % 2 == 1 )System.out.printf("#");
                    if( (i+j) % 2 == 0)System.out.printf(".");
                }
                System.out.printf("\n");
            }
            System.out.printf("\n");
        }
    }
}
