#include<stdio.h>

int main(){
int h,w,i,j;

while(1){
  scanf("%d %d",&h,&w);
  if(h == 0 && w == 0)break;
  for(i=0;i<h;i++){
  for(j=0;j<w;j++){
    if(i%2 == 0){
      if(j%2 == 0)printf(".");
      if(j%2 == 1)printf("#");
    }
    if(i%2 == 1){
      if(j%2 == 0)printf("#");
      if(j%2 == 1)printf(".");
  }
  printf("\n");
  }
  printf("\n");
}
return 0;
}