#include<iostream>
using namespace std;
int main()
{
	int H;
	int W;
	

	while (cin >> H >> W,H || W)
	{
		for (int i = 0; i < H; i++)
		{
			for (int j = 0; j < W; j++)
			{
				if ((i+j)%2==1)
				{
					cout << ".";
				}
				else cout << "#";
			}

			cout << endl;
		}

		cout << endl;

	}
	return 0;
}

