import java.util.*;

class Main {
	public static void main(String[] arg){
		Scanner in = new Scanner(System.in);
		while(true){
			int x = in.nextInt();	
			int y = in.nextInt();
			if (x == 0 && y == 0)break;
			StringBuilder sb = new StringBuilder();
			for(int i = 0;i < x;i++){
				for(int j=0;j < y;j++){
					if( (i%2 == 0 && j%2 == 0)||(i%2 == 1 && j%2 == 1)){
						sb.append("#");
					}
					else{
						sb.append(".");
					}
				}
				sb.append("\n");
			}
			System.out.println(sb);
		}	
	}