#include<bits/stdc++.h>
using namespace std;


int main()
{
  while(true)
  {
    int h,w;
    cin>>h>>w;
    if(h==0 && w==0) break;
    for (int i = 0; i < h; ++i)
    {
      for (int j = 0; j < w; ++j)
      {
        cout<<((i+j)%2==0? "#":".");
      }
      cout<<endl;
    }
    cout<<endl; 
  }
}
