#include<iostream>
using namespace std;

int main(){
    int h, w;
    while(1){
    cin >> h >> w;
    if( h == 0 || w == 0) break;
    for(int a = 0;a < h; a++){
     for(int b = 0;b < w; b++){
       if(a % 2 == 0){
???????????????if(b % 2 == 0) cout << "#";
          else cout << ".";
      } else{
          if(b % 2 == 0) cout <<".";
          else cout<< "#";
     }
   }
   cout<<endl;
  }
  cout << endl;
 }
  return 0;
}