#include<iostream>
using namespace std;

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

  return 0;

}