void paren(int tr[], int r)
{
 if ( r > LAST)
 {
  return;
 }
 if (tr[r] != -1)
 {
  printf("(%2d ", tr[r]);
  if (tr[r*2] == -1)
  {
   printf("()");
  }
  if (tr[r*2+1] == -1)
  {
   printf("()");
  }
  paren(tr, r*2);
  paren(tr, r*2+1);
  printf(" )");
 }
}