#include<iostream>
using namespace std;

int main()
{
	int H, W;
	while (true) {
		cin >> H >> W;
		if (H == 0 && W == 0)break;
		for (int i = 0; i < H; i++) {
			for (int j = 0; j < W; j++) {
				if ((i + j) % 2 == 0)cout << "#";
				else {
					cout << ".";
				}
			}
			cout << "\n";
		}
		cout << "\n";
	}
}
