#include <iostream>
using namespace std;

int main(){
	int H,W;
	while(cin >> H >> W){
		if(H==0&&W==0) break;	
		for(int i=0;i<H;i++){
			for(int j =0 ; j<W ; j++){
				if(i%2==0 && j%2==0 || j%2==1 && i%2==1) cout << "#";
				else cout << ".";
			}
			cout << "\n";
		}
		cout << "\n";
	}
}