#include<stdio.h>

int main(){
 int i,H,W,j;
 scanf("%d%d",&H,&W);
 while(H*H+W*W){
  for(j=0;j<H;j++){
   if(j%2){
    for(i=0;i<(W/2-1);i++){
     printf(".#");}
    if(W%2){
     printf(".");}
    else{
     printf(".#");}}
   else{
    for(i=0;i<(W/2-1);i++){
     printf("#.");}
    if(W%2){
     printf("#");}
    else{
     printf("#.");}}}
   printf("\n");}
  printf("\n");
  scanf("%d%d",&H,&W);}
 return 0;}