#include <iostream>
using namespace std;

void write(int w, bool flag);

int main(){
	int h, w = 0;
	bool flag = true;
	bool writeFlag = true;

	while(flag == true){
		cin>h>>w;

		if(h == 0 && w == 0) break;

		for(int j = 1; j < (h+1)/2; j+=2){
			write(w,true);
		}
		if(h%2 == 1) write(w,false);

	}
	flag = false;
}


void write(int w, bool flag){
	for(int i = 0; i < w/2;i++){
		cout<<"#.";
	}
	if(w%2 == 1)cout<<"#";
	cout<<endl;

	if(flag == true){
		for(int i = 0; i < w/2;i++){
				cout<<".#";
			}
			if(w%2 == 1)cout<<".";
			cout<<endl;
	}
}