#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int main() {
 int h, w;
 string line;

 cin >> h >> w;

 while(h != 0 || w != 0) {
  for(int i = 0;i < w;i++) {
   if(i % 2 == 0)
    line += "#";
   else
    line += ".";
   }

   for(int i = 0;i < h;i++) {
    cout << line << endl;
    reverse(line.begin(), line.end());
   }
  }
 
  cin >> h >> w;
 }

 return 0;
}