#include <iostream>
using namespace std;
 
int main() {
	int H,W;
 
	while(1){
		cin >> H >> W;
		if(H==0 && W==0)break;
		for(int i = 0; i < H; i++){
		for(int k = 0; k < W; k++){
			if((i+k)%2 == 0) cout << "#";
			else cout << ".";
		}	
		cout << "\n";
		}
		cout << "\n";
	}
	return 0;
}