#include <iostream>
using namespace std;
int main(){
int H,W;
cin>>H>>W;
while(1){
	if(H==0&&W==0)break;
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;
cin>>H>>W;
}
return 0;
}
