import java.io.*;

public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb;
        do{
            sb = new StringBuilder();
            
            String[] strs = br.readLine().split("\\s+");
            int height = Integer.parseInt(str[0]);
            int width = Integer.parseInt(str[1]);
            
            if(height == 0 && width == 0) break;
            
            for(int i = 0;i < height; i++){
                for(int j = 0;j < width; j++){
                    sb.append((i + j) % 2 == 0 ? "#" : ".");
                }
                sb.append("\n");
            }
            System.out.println(sb);
        }
        while(true);
    }
}