#include <iostream>
#include <algorithm>
using namespace std;
int main(){
	int a = 1, b = 1, i = 1;
	while ((a != 0)||(b != 0)){
		if (i != 1)
			cout << endl;
		i++;
		cin >> a >> b;
		if ((a != 0)||(b != 0))
			for (int i = 1; i <= a; i++){
				for (int j = 1; j <= b; j++){
					if ((i % 2 == 0)&&(j % 2 == 1)
						cout << '#';
						else if ((i % 2 == 1)&&(j % 2 == 0)
							cout << '#';
							else cout << '.';
				}
				cout << endl;
			}
	}
}
