#include<iostream>

using namespace std;

int main()
{
int x,y;

while (1)
{
cin >> x >> y;

if (x == 0 && y == 0)
break;

for (int i = 0; i < x; i++)
{
for (int j = 0; j < y; j++)
{
 if ((i + j) % 2 == 0)
  cout << '#';
 else
  cout << '.';
}
cout << endl;
}
cout << endl;
}
return 0;
}