#include<iostream>
using namespace std;
int main(void){
  int h,w,i,j;
  while(1){
    cin>>h>>w;
    if(h==0&&w==0)break;
    for(i=0;i<h;i++){
      for(j=0;j<w;j++){
	if((i%2==0&&j%2==0)||(i%2!=0&&j%2!=0)){
	  cout<<"#";
	}else{
	  cout<<".";
	}
      }
      cout<<endl;
    }
    cout<<endl;
  }
  return 0;
}