#include <iostream>
using namespace std;
int main(){
	int i, j,x,H,W;
	for (;;){
		cin >> H >> W;
		if (H == 0 && W == 0)break;
			for (j = 1; i == H; j++){

				x = i + j;
				if (x % 2 == 0){
						cout << ".";
				}
				if (x % 2 != 0){
						cout << "#";
				}
				if (j == W){
					cout << endl;
					i++;
			}
	}





	return 0;
}