#include<stdio.h>
int main(){
int H,W,h,w;
while(1){
scanf("%d%d",&H,&W);
if(H == 0 && W == 0)break;
for(h = 1;h <=H;h++){
  for(w = 1;w <=W;w++){
    if(h%2==1){
      if(w%2==1)putchar('#');
      else putchar('.');}
    else{
      if(w%2==1)putchar)('.');
      else putchar('#');}
  putchar('\n');}
putchar('\n');}
return 0;
}

