#include<iostream>
using namespace std;
int main(){
	int h, w, i, j;
	while (cin >> h >> w, h || w){
		for (i = 0; i < h;++i){
			for (j = 0; j < w; ++j)
				cout << ((i % 2) ? ((j % 2) ? "#" : ".") : ((j % 2) ? "." : "#"));
			cout << endl;
		}
		cout << endl;
	}
}