#include<iostream>
using namespace std;
int main(){
  int i,j,H,W;
  while(true){
    cin >> H >> W;
    if(H==0 && W==0)break;
    for(i=1;i<=H,i++){
      int a=i/2;
      if(i==2*a+1){
        for(j=1;j<=W;j++){
          int b=j/2;
          if(j==2*b+1){
            cout << "#";
          }else{
            cout << ".";
          }
        }
        cout << endl;
      }else{
        for(j=1;j<=W;j++){
          int c=j/2;
          if(j==2*c+1){
            cout << ".";
          }else{
            cout << "#";
          }
        }
        cout << endl;
      }
    }
    cout << endl;
  }
}