import java.util.*;
public class Main {
	public static void main(String[] args) {
		 Scanner scan = new Scanner(System.in);
		 int H;	//縦
		 int W;	//横
		 while(true){
			 H = Integer.parseInt(scan.next());
			 W = Integer.parseInt(scan.next());
			 if(H == 0 && W == 0){
				 //HとWが0の時、終了。
				 break;
			 }//if
			 //--- 出力 ---
			 for (int i = 0; i < H; i++ ){
				 for (int j = 0; j < W; j++ ){
					 if((i + j) % 2 == 0){
						 //(i+j)/2の答えが奇数だったら"#"、偶数だったら"."
						 System.out.print("#");
					 }else{
						 System.out.print(".");
					 }//if
				 }//for
				 System.out.println();
			 }//for
			 System.out.println();
		 }//while 
	}
}
/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