#include <string>
using namespace std;

int main()
{
  int H, W;

  while( 1 ) {
    cin >> H >> W;
    if( H == 0 and W == 0 ) {
      break;
    }

    string buf1 = "";
    string buf2 = "";
    for( int i = 0; i < W; i++ ) {
      if( i % 2 == 0 ) {
        buf1 += "#";
        buf2 += ".";
      }
      else {
        buf1 += ".";
        buf2 += "#";
      }
    }

    for( int j = 0; j < H; j++ ) {
      if( j % 2 == 0 ) {
        cout << buf1 << endl;
      }
      else {
        cout << buf2 << endl;
      }
    }
    cout << endl;
  }
  return 0;
}