#include <iostream>
using namespace std;

int main() {
int a, b = 5;
while(1) {
cin >> a >> b;
if (a == 0 && b == 0) {
break;
}
for (int i = 0; i < a; i++) {
for (int j = 0; j < b; j++) {
if (i % 2 == 1) {
if (j % 2 == 1) {
cout << "#";
}else {
cout << ".";
}} else {
if (j % 2 == 1) {
cout << ".";
}else {
cout << "#";
}
}
}cout << endl;
}} cout << endl; }
return 0;
}
