import java.util.Scanner;
class Main {
 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  while(true) {
   int H = sc.nextInt();
   int W = sc.nextInt();
   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){
      System.out.printf("#");
     }else{
      System.out.printf(".");
     }
    }
    System.out.println();
   }
System.out.println();
  }
 }
}
