import std.stdio;
void main() {
	int h, w;
	for (;;) {
		"%d %d\n".readf(&h, &w);
		if (h == 0 && w == 0) break;
		foreach (j; 0..h) {
			foreach (i; 0..w) {
				if (i % 2 == 0 && j % 2 == 0 || i % 2 == 1 && j % 2 == 1)
					"#".write;
				else
					".".write;
				if (i == w - 1) "".writeln;
			}
		}
		"".writeln;
	}
}