#include<iostream>
using namespace std;

int main(){

   int i,j,H,W;

   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+j)%2 == 0){
				cout << "#";
			}else{
				cout << ".";
			}

		}

		cout << endl;

	}

	cout << endl;

   }

   return 0;
}