#include<iostream>

using namespace std;


int main(){

	int H,W;
	while(true)
	{
		cin >> H >> W;

		if(H+W == 0) break;

		for(int i=0;i<H;i++)
		{
			for(int k=0;k<W;k++)
			{
				if((i+k)%2 == 0) cout << "#";
				else cout << ".";
			}
			cout << "\n";
		}
		cout << "\n";

	}
	return 0;
}
