# Erase half of '1's

( '1', 0) = ( 'Z', 1, >)
( '1', 1) = ( 'Z', 2, >)
( '1', 2) = ( '1', 2, >)
( '1', 3) = ( '1', 3, >)
( '1', 4) = ( '1', 4, <)
( '1', 5) = ( '1', 5, <)

( 'Z', 0) = ( 'Z', 0, <)
( 'Z', 2) = ( 'Z', 3, >)
( 'Z', 3) = ( '1', 4, <)
( 'Z', 4) = ( 'Z', 5, <)
( 'Z', 5) = ( 'Z', 0, >)
