% perl diffN.pl
( 0 0 0 )
( 1 - 1 )
( 2 - )
( 3 - )
( 4 - )
( - 1 )
( - 2 2 )
( - - 3 )
( - - 4 )
( - 3 )
( - 4 )
( - 5 5 )
( - - 6 )
( 5 6 7 )
( 6 7 8 )

( a b d e f - - - - - - - - h i )
( a - - - - z c - - d f g - h i )
( a b - - - - c j k - - g n h i )

 % perl diffN.pl tye says japhy asked
( - - 0 )
( - 0 )
( - 1 1 0 )
( - - 2 )
( - - 3 )
( 0 - - )
( 1 2 4 )
( - 3 - 1 )
( - - - 2 )
( 2 - - 3 )
( - - - 4 )

( - - - - - t y - - e - )
( - s a - - - y s - - - )
( j - a p h - y - - - - )
( - - a - - - - s k e d )