sub Merge(@) {
    my @array = @_;
    MergeSort (\@array, 0, $#array);
    return @array;
}
sub MergeSort($$$) {
  my $arrref = shift;
  my $first = shift;
  my $last = shift;
  if ($last>$first) {
    my $mid = int(($last+$first)/2);
    MergeSort($arrref, $first, $mid);
    MergeSort($arrref, $mid+1, $last);
    my @b;
    
    @b = ( @{$arrref}[$first..$mid], @{$arrref}[reverse($mid+1..$last)] );
    my ($i, $j, $k) = (0, $last-$first, $first);
    for (; $k<=$last; $k++) {
      $arrref->[$k] = ($b[$i]<$b[$j]) ? $b[$i++] : $b[$j--];
    }
  }
}