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