#include<iostream>
using namespace std;

int main(){
	int H, W;
	while (true){
		cin >> H >> W;
		if (H == 0 && W == 0)break;
		for (int i = 1; i <= H; i++){
			for (int j = 1; j <= W; j++){
				if ((i-j) % 2 == 0)cout << "#";
				else cout << ".";
			}
			cout << endl;
		}
		cout << endl;
	}
	return 0;
}