#include<iostream>
using namespace std;

int main(){
   int H,W;
   
   while(true){
       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%2 == 1){
                   if(j%2 == 1){
                       cout << "#";
                   }else if{
                       cout << ".";
                   }
               }else if{
                   if(j%2 == 1){
                       cout << ".";
                   }else if{
                       cout << "#";
                   }
               }
           }
       }
       cout << endl;
   }
   return 0;
}