//itp1_topic1_a
#include <bits/stdc++.h>
using namespace std;

int main(){
 while(1){
 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++){
 if((i+j)%2==0)cout<<"#";
 else cout<<".";
 }
cout<<endl;
}
cout<<endl;
}

}
