#include<iostream>
using namespace std;

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