import std.stdio,
       std.range,
       std.conv;
import std.math;

void main(){
	int w, h;
	while(true){
		scanf("%d %d", &h, &w);

		if(h == 0 && w == 0) break;
		foreach(i; 0..h){
			foreach(j; 0..w){
				write(((i+j)%2) ? "." : "#");
			}
			writeln();
		}
		writeln();
	}
}