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