use strict;
   use warnings;
   
   my $num4g = 2 ** 32; my $grt4g = 500_000 + $num4g ;
   my $start = $num4g - 50; my $no = 0;
   while ( 1 )
   {  my $no1 = Pack( $start );
      my $result = UnPack( "$no1" );
      if ( $start != $result ) { die "not match"; }
      $start++; $no++;
      if ( $start >= $grt4g ) { print "Okay ( $no )\n"; exit; }
   }
   
   sub Pack
   {  my $input = shift;
      my $lower = $input % $num4g;
      my $upper = int ( $input / $num4g );
      return ( pack("N N", $upper, $lower ) );
   }
   
   sub UnPack
   {  my $input = shift;
      my ( $upper, $lower ) = unpack("N N", $input);
      return ( ( $upper * $num4g ) + $lower );
   }
   
   
   1;