#include <iostream>
using namespace std;

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