#include <iostream>

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