
#include <iostream>
using namespace std;

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