#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;
  }
  return 0;
}

