import java.io.*;

public class Main{
	public static void main(String[] args)throws IOException, NumberFormatException{
		BufferedReader br = new BufferedReader (new InputStreamReader(System.in));
		StringBuilder builder = new StringBuilder();
		
		while(true){
			String[] s = br.readLine().split(" ");
			int h = Integer.parseInt(s[0]);
			int w = Integer.parseInt(s[1]);
			if( h==0 && w==0 ) break;
			
			// ???????????°?????????
			for( int i=1 ; i<=h ; i++ ){
				// ????????°?????????
				for( int j=1 ; j<=w ; j++ ){
					if( i%2==1 ){
						if( j%2==1 ){					
							builder.append("#");
						}else{
							builder.append(".");
						}
					}else{
						if( j%2==0 ){
							builder.append("#");
						}else{
							builder.append(".");
						}
					}
				}//???
				builder.append("\n");
			}//??????
			builder.append("\n");
		}
		System.out.print(builder);
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz