#include<bits/stdc++.h>
using namespace std;
int main(){
  int h,w;
  while(cin>>h>>w,h+w!=0){
    for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
        cout<<(((i+j)%2==0)?"#":".");
      }
      cout<<endl;
    }
    cout<<endl;
  }
}
