#include<bits/stdc++.h>
using namespace std;
int main(){
	int r,c;
	while (cin >> r >> c){
		if (!(r | c)) break;
		for (int i=0;i<r;i++){
			for (int j=0;j<c;j++){
				cout << (((i + j)%2 == 0) ? '#' : '.');
			}
			cout << endl;
		}
		cout << endl;
	}
}
