main(require('fs').readFileSync('/dev/stdin', 'utf8').replace(/\r?\n$/, "").split(/\r?\n/));

function main(lines){
	lines.map(function(s){return s.split(" ").map(Number)}).every(function(a){
		h = a[0]; w = a[1];
		if(h+w == 0) return false;
		for(var y=0;y<h;y++){
			var str = "";
			for(var x=0;x<w;x++){
				str += (x+y)%2==0 ? "#" : ".";
			}
			console.log(str);
		}
		console.log();
		return true;
	});
}