#include <iostream>
#include <string>
#include <vector>
#include <stdio.h>
using namespace std;
#define C


#ifdef C
int main(void)
{
	int H, W;
	vector<pair<int, int> > arr;
	while (true)
	{
		cin >> H >> W;
		if (H == 0 && W == 0) break;
		arr.push_back(pair<int, int>(H, W));

	}
	for (auto a : arr) {
		for (size_t i = 0; i < a.first; i++)
		{
			bool f = (i % 2 == 0) ? true : false;
			for (size_t j = 0; j < a.second; j++)
			{
				if (f)
					cout << "#";
				else
					cout << ".";
				f = !f;
			}
			cout << endl;
		}
		cout << endl;
	}
	return 0;
}