include<iostream>
using namespace std;

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