#include <iostream>
using namespace std;

int main()
{
while(true){	
		int H,W,k=0;
		cin>>H>>W;
		if(H==0&&W==0) break;
		while (k<H)
		{	
			for(int i=0;i<W;i++){
				if(k%2==1&&i%2==1||k%2==0&&i%2==0)cout<<"#";
				else cout<<".";
			}
			cout<<endl;
			k++;
		}
		cout<<endl;
	}
   return 0;
}
