message:Without using switches, design a mechanism that takes an arbitrary stream of boulders as input (with at least some minimum spacing between adjacent boulders) and outputs only the even (or odd) boulders in the sequence.
message1:Improved solution by zugz
NNNO       N
NNNNNNNNNN=N
NNNNNNNNNN N
NNNNNNN    &
NNNNNNN NN =
NNNNNNN   &&&&&&
NNNNNNNN N (((((
NNN        N
NNN NNNNN  N
"   NNNN"  "
NNNNNNNNNNNN
Q    1    @N