HDTenEightyP/NetNews huggingface dataset:
Newsgroups: rec.games.chess,rec.games.go,rec.games.board,rec.games.programmer
Subject: Nine Men's Morris [Re: Awari?]
From: elkies@ramanujan.harvard.edu (Noam Elkies)
Date: 21 Aug 92 11:24:08 EDT
Organization: Harvard Math Department
Keywords: Nine Men's Morris
Summary: counting positions

In article <darse.714370337@silver-vly>
darse@cs.UAlberta.CA (Darse Billings) writes:
>elkies@ramanujan.harvard.edu (Noam Elkies) writes:
>
>>Nine Men's Morris!?  Surely *that* is completely solved by now?
>>There are only about 18 billion possible positions modulo the
>>8 board symmetries.
>
>Well, not to my knowledge.  Umm, I count 3^24 = 282429536481 or about
>10^12 board positions without symmetries -- am I missing something?

For one thing, that's only about quarter of 10^12.  For another thing,
that counts all ways of making each of the 24 points White, Black, or
empty; but not all of them are legal positions, since there is the
constraint that the total numbers of White and Black men not
exceed 9.  [At least in the version of the game I know: begin by
alternately placing 9 men of both colors on the board; then alternately
move along the lines, removing an opponent's piece of your choice
whenever a monochromatic 3-point line is achieved --- so one never
has more than 9 men of the same color on the board.]  Given the numbers
w,b of White and Black men, the number of possible positions is
(24-choose-w)([24-w]-choose-b)=24!/(w!b!(24-w-b)!); summing this over
100 possible values of (w,b) from (0,0) to (9,9) gives 143122694691.
I then divided this number by 8, but in Nine Men's Morris there is
the additional symmetry of exchanging the inner and outer ring, so
I should have divided by 16 to get about 9 billion positions.  [The
number of positions symmetrical under any one of these symmetries is
negligible so just dividing by 16 gives a very good approximation.]
This is about the same as the number of positions in a 6-piece chess
endgame without repeated pieces; such endgames are tractable, albeit
barely, by current technology (L.Stiller).

--Noam D. Elkies (elkies@zariski.harvard.edu)
 Dept. of Mathematics, Harvard University

Newsgroups: rec.games.chess
From: nates@ll.mit.edu ( Nate Smith)
Subject: Re: human vs. machines
Organization: MIT Lincoln Laboratory
Date: Wed, 12 Aug 92 13:04:25 GMT

In article <SCHILLER.92Aug11214713@tira.uchicago.edu> schiller@tira.uchicago.edu (Eric Schiller) writes:
>
>The idea of allowing humans to use books against machines
>was discussed.
>I pointed out that if I were given access only to those books
>I have written, I would gain several hundred points in strength,
>since I am famous for not remembering stuff! And indeed, it might
>be fun. But while I would enjoy this in an exhibition (or an
>amateur event, which is pretty much the same for me), I doubt that
>I would feel comfortable playing under these rules in a serious event.
>
>Eric Schiller

indeed, would Kasparov agree to play Fischer if Fischer stipulated that
he gets to have anywhere from 4-10 constant advisors, possibly even
including Kasparov himself!, and a large library of open books, with a
librarian attendant constantly at the ready, while Kasparov has only
his mind and his 2 bare hands.

i am sure this discussion has come up before, but since i am new here,
i'll put it thus:  computers are disqualified from such tournaments as
the U.S. Open, because they violate the basic concept of 1-on-1.

go ahead and have them play people all you want, but they are committees
of software engineers and topnotch players, not individuals.

- nate, who never did fully like those "open book" tests, either....
From: mkukkone@klaava.Helsinki.FI (Mika Kukkonen)
Newsgroups: rec.games.chess
Subject: Re: Torre Attack
Date: 19 Aug 92 04:08:57 GMT
Organization: University of Helsinki

In <1992Aug18.195610.26069@colorado.edu> perlman@qso.Colorado.EDU (Eric S. Perlman) writes:

>An interesting, and related discussion to this thread would bear on the
>relative worth and results of the Veresov and Torre, as well as hybrid
>systems between the two.  Anyone want to bite?

I'll give it a start :). I have myself played these "anti-Indian"
defences quite a lot, and they are not so bad, but black can usually
equalises easily if he knows what he is doing:

Veresov
1.d4 d5 2.Nc3 Nf6 (2.-Bf5!? is also interesting) 3.Bg5 Nbd7 (IMHO the
best move) 4.Nf3 (4.f3 c6 5.e4 dxe4 6.fxe4 e5! 7.dxe5 Da5 is =+. I have
tried 5.Qd2, with mediocre results.) g6 and black has easy development
and can usually achieve equalising (at least) e5-push. Only way white
can try for advantage is playing e4, but after exchanges in e4 there is
not much play left.

Trompovsky
1.d4 Nf6 2.Bg5 c5 (2.-d5 3.Bxf6 exf6 should give white some play, but I
all my kingside attacks have failed awfully) 3.d5 (3.Nc3!? cxd4 4.Qxd4
Nc6 5.Qh4 is unclear after opposite castling, but I think blacks attacks
is at least as fast as white. 3.Bxf6 gxf6 4.d5 Qb6 5.Qc1 might give
white some chances also.) Ne4 4.Bf4 (4.Bh4 and 4.Bc1 are alternatives.)
Qb6! and now 5.Qc1 gives black equality, so I have toyed with Piket's
gambit 5.Nd2, again with bad result. Simple line: 5.-Qxb2!? 6.Nxe4 Qb4+
7.Qd2 Qxe4 8.f3 and white does have some compensation, but is it enough?

Torre
1.d4 Nf6 2.Nf3 e6 3.Bg5 c5 4.e3 Be7 (4.-Qb6 is in fashion, but
gambitting the b-pawn should give white good compensation.) 5.Nbd2 b6
6.Bd3 Bb7 7.O-O O-O (I gave a line with 7.-Nc6 in my last post, witch
seemed ok for black also) 8.c3 d6 9.Re1 cxd4 10.exd4 Nbd7 and black has
comfortable game.

Torre vs. KI
1.d4 Nf6 2.Nf3 g6 3.Bg5 Bg7 4.Nbd2 d6 (4.-d5 is alternative route to
equality) 5.e4 O-O 6.c3 c5 (6.-Nbd7 and e5 to come is main line, but
this is easier) 7.dxc5 (7.Bd3 cxd4 8.cxd4 Nc6 =) dxc5 8.Be2 (8.Bc4 Nc6
9.O-O Qc7 10.Qe2 Na5! =) Nc6 9.O-O b6 10.Qc2 Bb7 with equality.

So, any improvents/suggestions for white?

Mika
-- 
Mika Kukkonen = Mika.Kukkonen@Helsinki.FI
Trying to learn to live in Helsinki University of Computer Science.
"I am studying, so I am, or am I (studying)?"
Newsgroups: rec.games.chess
From: perlman@qso.Colorado.EDU (Eric S. Perlman)
Subject: Re: Suggestions for chess program?
Organization: University of Colorado, Boulder
Date: Mon, 17 Aug 1992 17:03:59 GMT

In article <1992Aug17.164657.27653@cs.brown.edu> jhc@iris.UUCP (James H. Coombs) writes:
>In article <2a8d4bfdwnr070@ark.abg.sub.org> ralf@ark.abg.sub.org (Ralf Stephan) writes:
>
>>But if he later buys a faster PC, he won't have a stronger program.
>>I recommend M-Chess (about U$100-150) that plays at Mach III level
>>even with a 286 with 12 MHz.
>
>A faster PC enables the program to search deeper in the same amount of
>time.  If you set the level to a fixed depth, then the playing strength
>will not change with the power of the machine: only the speed of the
>search will vary.  The difference between Zarkov 2.6 on my XT at about
>9 MHz and my 80486 at 25 MHz is approximately 1+ ply.  Now this is a
>very rough estimate based on watching the two at the same time: one
>bogs down at 6 ply and the other at 7-8 ply (depending on the position
>and on how closely you are watching, etc.).
>
>More precisely, CCR adds 60 points to 386/33 results to get an
>estimated result for 486/33.  I don't know what adjustment to make for
>a 286/12.  In any case, the speed of the machine does affect the
>strength of the program when set at time control instead of depth
>control.

If the relation is linear with processing speed, then there is relevant
data in PC magazine, July 1992, relating the direct processing speed of
computers even across 80286/80386/80486 barriers, at least for the
intel-based compatibles.

From memory, the increase in processing speed from a 9 MHz AT to a 25
MHz 80486SX is roughly a factor of 12 (but you can check me on this).

-- 
"How sad to see/A model of decorum and tranquillity/become like any other sport
A battleground for rival ideologies to slug it out with glee." -Tim Rice,"Chess"
     Eric S. Perlman 				 <perlman@qso.colorado.edu> 
  Center for Astrophysics and Space Astronomy, University of Colorado, Boulder
From: Bruce_Harper@mindlink.bc.ca (Bruce Harper)
Newsgroups: rec.games.chess
Subject: Re: Correction! (Bishops and Queens)
Date: 22 Aug 92 19:12:29 GMT
Organization: MIND LINK! - British Columbia, Canada

Why is it cheating to have a position where retroanalysis proves whose move it
is?  This is precisely what's involved in the Bishop wins - Queen loses
problem.  The position is a legal one, but not one that would ever occur in a
game (I don't know if anyone has ever had to promote to a Bishop in an actual
game).
Newsgroups: rec.games.chess,rec.games.go,rec.games.board,rec.games.programmer
From: quirk@pioneer.unm.edu (Gym Z. Quirk)
Subject: Re: rec.games.strategic
Date: Fri, 21 Aug 92 22:15:45 GMT
Organization: Space and Planetary Image Facility

In article <5773@vexpert.dbai.tuwien.ac.at> mst@vexpert.dbai.tuwien.ac.at (Markus Stumptner) writes:
>From article <v__n=0@lynx.unm.edu>, by quirk@pioneer.unm.edu (Gym Z. Quirk):
>> Furthermore, when I think of 'strategic' games, I tend to think of
>> 'strategic level military simulations'.  
>
>This argument was ruled invalid already earlier in the discussion
>(i.e., before it included rec.games.board), because you can't prove
>that 99% of Usenet readers think like you do.

Well, if you had included the next sentence of my post, you wouldn't
have had to make the above statement.

For the records I'll re-include it here.

> (But that's just my twisted little mind.)

Also, how should I be expected to know what occured before this
discussion reached rec.games.board when I first encountered it on
rec.games.board?

>Markus Stumptner                                mst@vexpert.dbai.tuwien.ac.at
>University of Technology Vienna                 vexpert!mst@relay.eu.net
>Paniglg. 16, A-1040 Vienna, Austria             ...mcsun!vexpert!mst


-- 
Capt. Gym Z. Quirk  (Known to some as Taki Kogoma)  quirk@pioneer.unm.edu
 I'll get a life when someone demonstrates that it would be superior to
                          what I have now...
Newsgroups: rec.games.chess
From: scridd@lims01.lerc.nasa.gov (JEFFREY RIDDLEBAUGH)
Subject: Re: 1. A4   WARE OPENING
News-Software: VAX/VMS VNEWS 1.41    
Organization: NASA Lewis Research Center
Date: 13 Aug 1992 15:39 EST  

In article <1992Aug9.205132.9300@uoft02.utoledo.edu>, dweddin@uoft02.utoledo.edu writes...
>>> 
>>> Maybe he'll write a book, "White to play and win with 1. a4!"  :) :) :) :)
>>> 
>>> John
>>> 
>>>
>> 
>>  
>> 	My friend actually found this opening in a book once.  It was listed
>> as the Ware Opening( anyone got any other info?).  He was especially interested
>> in this because his last name is Ware.
>> 
>> 							Greg
> 
>i saw this opening is a book a LONG TIME ago.... don't ask which one...
>but the book referred to it as the 
> 
>    "crab opening"
> 
>never seen it since or ever heard of it as the WARE OPENING.
> 
> 
>if anybody knows of any books on it....please post.
> 
>don wedding
> 
> 
> 
It's named for a 19th century player named Preston Ware, who played
1. a4 or 1... a4 quite a lot.  1. a4 is also called the Meadow Hay
Opening.
Newsgroups: rec.games.chess,rec.games.go,rec.games.board,rec.games.programmer
From: gl8f@fermi.clas.Virginia.EDU (Greg Lindahl)
Subject: Re: rec.games.strategic
Followup-To: news.groups
Keywords: checkers, shogi, othello, hex, etc.
Organization: Department of Astronomy, University of Virginia
Date: Fri, 21 Aug 1992 05:23:44 GMT

In article <gardner.714363742@bruce.cs.monash.edu.au> gardner@cs.monash.edu.au () writes:

>There is a class of games you do not consider that would fit perfectly
>into such a group: bargaining games! 

Isn't Diplomacy a bargaining strategy game? Isn't Diplomacy routinely
discussed on rec.games.board? Sounds like you'd be totally welcome to
use rec.games.board for these discussions, as was suggested the last
20 times this topic came up. It's not like rec.games.board has a high
volume to discourage you.

Followups to news.groups, which is the "right place" for discussions
about new groups.
Newsgroups: rec.games.chess
From: phillies@wpi.WPI.EDU (George D. Phillies)
Subject: Chess, a game of peace
Organization: Worcester Polytechnic Institute
Date: Wed, 19 Aug 1992 03:09:55 GMT

Let's see: the former world champion is credited with a 
(perhaps mythical) book entitled  "CRUSH your opponent with..."
The only machine opponent to be given a mechanical arm had
the quaint habit of crunching captured pieces, reducing 
them to power.  The best female player in the world has taken 
up kick boxing for physical conditioning.  Also, chess is an 
intellectual, non-violent hobby, suitable for those of placid
temperament.

More seriously, I recently purchased Grandmaster Chess
(Capstone).  Has anyone tested its ranking against other
programs or opponents?  (I have yet to beat it, which
only proves that its ranking is up there in the three
digit range someplace.  (8^)=)

George Phillies
phillies@wpi.wpi.edu
From: direwolf@seismo.gps.caltech.edu (Kathy Watts)
Newsgroups: rec.games.chess
Subject: Re: US Open
Date: 13 Aug 92 05:48:39 GMT
Organization: California Institute of Technology, Pasadena

In article <1992Aug12.195537.29357@cs.brown.edu> jhc@iris.brown.edu.UUCP (James H. Coombs) writes:
>In article <1992Aug12.175836.21990@cco.caltech.edu> direwolf@seismo.gps.caltech.edu (Kathy Watts) writes:
>>(please reply to Hal Bogner, direwolf@seismo.gps.caltech.edu)
>
>>Richard Lang's, for instance), it's hard to avoid the conclusion that
>>the best way to find out how much progress one has made is by trying it
>>out against people.  And tournaments are where those people are!
>
>Why not play computers against computers that have already been rated.
>Computers can play in a separate rating pool, and we already have
>enough rated machines to seed the pool.  And professional players have
>already demonstrated a willingness to participate from time to time to
>provide some correlation with the pool of people.

Sorry, Jim, but I must have been to vague here.  Playing in tournaments isn't
about "getting a rating."  It's about seeing how well the program is able to do
what humans do at chess (as well as what computers do).  And few programs
really require the tiny, elite group of professional players to point their
flaws out.
>
>Most of us care primarily about the strengths of machines relative to
>each other (and cost, features, etc.).  And a developer can certainly
>sit there bench marking a program against a Mach III or the like for
>the testing process.
>
>--Jim

Here I really have to differ!  I think that there's already altogether too much
emphasis on the incestuous "which machine beats which other machine" front.
What if the "best" machine were "uninteresting to play," or lacked other useful
features?  I know I am not a typical publisher of chess software - I don't care
to engage in the ratings debate, and have been very slow to promote Zarkov's
success in competition.  As a chessplayer for 20 years, I care more about the
users desires than which one kicks whose butt faster.  The worst product, in my
opinion, is the one which plays the same way over and over, and ends up
collecting dust on a shelf after the initial enjoyment wears off.  I had the
good fortune to work as Dave Kittinger's chess advisor a decade ago, and helped
him to overcome this problem in the Novag Constellation.  Novag's founder,
Peter Auge, cited that particular model as the one that first proved that chess
computers could play a "human-like" game.  I was proud when I read that.  If I
had lived by the formula expressed above, I couldn't have done that.

Thanks for helping me to express that!

Best,

Hal Bogner
Newsgroups: rec.games.chess
From: jarmo@ae.tut.fi (Jarmo Sorvari)
Subject: Re: Piket-van Mil
Organization: Tampere Univ. of Technology, Finland.
	<1992Aug17.225310.10561@cbnewsh.cb.att.com>
	<16u3q0INN10j@iraul1.ira.uka.de>
Date: 20 Aug 92 10:12:27


In article <16u3q0INN10j@iraul1.ira.uka.de> preiss@i31s15.ira.uka.de (Martin Preiss) writes:
> In article <1992Aug17.225310.10561@cbnewsh.cb.att.com>, gls@windmill.att.com (The Human Windmill) writes:
> |> In <28536@option.GBA.NYU.EDU>, mginsbur@option.GBA.NYU.EDU writes:
> |> > Hello, would someone with a reasonable 
> |> > computer like to try this position:
> |> > 
> |> > 1. Nf3 f5
> |> > 2. e4  fe
> |> > 3. Ng5 d5
> |> > 4. d3  Qd6

>  As far as I know a good alternative is still:
>  5. dxe4  h6
>  6. Qh5+  g6
>  7. Qh4   Bg7
>  8. Nf3   +=/=
>  Has anybody new games or insights for this position ?

No games, but I looked at this position once, expecting one of my
friends to play it.  I thought then, that I might even like this
position as Black, trying 8... g5!?.  The white queen will lose some
time (or alternatively is pushed to attack :-)).  For example: 9. Qh5+
Kf8 10. Bd3? (10. ed5? Bf5 and 11... Nf6) 10... Nf6 11. Qg6 de4 12.
Be4 (12. Bc4 Be6) 12... Qb4+ 13. Nc3 Ne4 14. Qe4 Bc3+ winning.  I
don't think white has any compensation for the pawn after 8... g5!? 9.
Qg3 Qg3 10. hg3 de4.

Is not also 8... Bf6 interesting for Black?
--
-----------------------------------------------------------------------------
! Jarmo Sorvari                         Control Engineering Laboratory      !
! jarmo@ae.tut.fi                       Tampere University of Technology    !
--------------------------------------- BOX 527, 33101 Tampere, Finland -----
Newsgroups: rec.games.chess
From: perlman@qso.Colorado.EDU (Eric S. Perlman)
Subject: Re: handicap in chess
Organization: University of Colorado, Boulder
Date: Thu, 20 Aug 1992 17:13:31 GMT

In article <PGH.92Aug20124621@gorby.cs.brown.edu> pgh@cs.brown.edu (Paul Howard) writes:
>One other way of giving a handicap that works well for a series of
>speed chess games is to change the time limit.  For instance, in a
>series of "5-minute" chess games, there are always 10 minutes alloted
>to the game, but whenever one player wins, he gives one minute to the
>other player; so for instance, the second game would be 6 minutes to
>4, the loser of the first game getting the extra time.  If the players
>are reasonbly close, they soon "find" a comfortable level (a level
>level, so to speak).

About eight years ago I played in an unrated tournament with just such a
time handicap based on ratings.  The nominal TC was G/120, but there was
a sliding scale, with the lower-rated player getting more time and the
higher rated player less time based on rating (I believe that the scale
was linear, and deducted 1 minute for every 10 rating points, or
something close to that).  The tournament did not produce any huge
surprises in results (and it was an 8 person RR), but it had at least
its share of upsets.


-- 
"How sad to see/A model of decorum and tranquillity/become like any other sport
A battleground for rival ideologies to slug it out with glee." -Tim Rice,"Chess"
     Eric S. Perlman 				 <perlman@qso.colorado.edu> 
  Center for Astrophysics and Space Astronomy, University of Colorado, Boulder
From: "jay hack" <jay.hack@execnet.com>
Newsgroups: rec.games.chess
Subject: chess news        5/5
Date: 17 Aug 92 03:12:45 EST
Reply-To: "jay hack" <jay.hack@execnet.com>
Distribution: rec
Organization: Executive Networks Information

>>> Continued from previous message
   Yugoslav  chess  champion Svetozar Gligoric told the paper
Spassky was  determined for revenge.
   ''I'm ready. I will put up a major retaliation for the defeat in
Reykjavik 20  years ago,'' he quoted Spassky as saying.

   The Belgrade businessman who lured Fischer from his self-imposed
exile to  play Spassky has denied the match was in any way intended
as a boost for the  embattled regime of Serbian President Slobodan
Milosovic.

   ''I've got nothing to do with politics, nothing to do with
Milosovic,''  Jezdimir Vasiljevic told Reuters last month.

   He added that it had taken 10 months to persuade 49-year-old
Fischer to  return to competition.

   ''It was very hard to convince him,'' he said.

   Fischer's movements in Yugoslavia have been surrounded by
secrecy amid  unconfirmed rumours that the slender, neatly groomed
young champion of the 1970s  now looked like an overgrown hippy.

   Journalists who tried to get a view of Fischer at Sveti Stefan
last month  said the former champion was surrounded by a battalion
of security guards who  even accompanied him swimming and warned
reporters to stay away.

   ''Any picture that appears in the papers is a problem. Why? I
have no idea,''  Vasiljevic said.

   ''What he told me was that publicity in the past had many times
interfered in  his private life, and there had been many stories
which were untrue, that's why  he was angry.''
---
  SLMR 2.0  Hit any key with hammer to continue
--
Executive Network Information System  (914) 667-4567
International ILink Host
Newsgroups: rec.games.chess
From: hau4@ellis.uchicago.edu (sven  hauptfeld)
Subject: Re: Fischer-Spassky and rating points
Reply-To: hau4@midway.uchicago.edu
Organization: University of Chicago Computing Organizations
Date: Tue, 18 Aug 1992 04:48:30 GMT

In article <92230.165832U55342@uicvm.uic.edu> <U55342@uicvm.uic.edu> writes:
>
>     Gligoric was (and perhaps still is!) The Dude, The "King" in the name
>     "King's Indian Defense!" You know the Classical main line of KID, the one
>     that goes 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 00 6.Be2 e5 7.00 Nc6
>     8.e5 Ne7-this should have been named after Gligoric and not Mar del Plata!
>

It should - but, in a way, it is! It was Gligoric who found the right plan for
black (...Rf7, ...Bf8, ...Rg7 or h7) in the tournament in Mar del Plata (1953?)
and thus it became known as "Mar del Plata". There is a Gligoric variation, too.

Sven

Newsgroups: rec.games.chess
From: os9ug@gkcl.ists.ca (OS-9 User Group)
Subject: Re: Fischer/Spassky time control
Reply-To: sizone!justin@ee.ryerson.ca  (Justin)
Organization: y
Date: Mon, 17 Aug 92 07:27:13 GMT

In article <1992Aug14.142620.46@wsuhub.uc.twsu.edu> bagai@wsuhub.uc.twsu.edu writes:
>I am told that the upcoming match will use Fischer's clock with the
>following time control:
>
>	Each player initially gets 90 minutes on his clock and an
>	additional 2 minutes after each move is made.
>
>	No secondary time controls, no adjournments, no nothing ....
>
>The only advantage that immediately comes to my mind is that this avoids
>mad time scrambles, because you always have at least 2 minutes before
>each move.  Can anyone think of any other benefit?
>
This is very similar to the time system used in Go.  

The advantage is that if you have a "victory on the board" but you have
run out of time, you are given a chance to prove it.  But if you have
wasted your time and have not got a clear win, your opponant will make
use of his time advantage to trap you, and you will be sorely penalized.

The theory is that if you have a "clear win", then you will not have to
think much about your moves, since it is so "clear".  But if it is
unclear, the short amount of additional time will not give you enough
time to make up lost ground, and you should lose.

In Go the system is actually to give each side 90 minutes, and then
when this runs out add on another time period called "byomi time".  
During byomi time you must make (usually) 25 moves within 10 minutes.
If you succeed in doing so, then a new period starts and you have to
make 35 moves in 10 minutes.  Every time you succeed, you get a new
period, but 10 additional moves to make in it.  

Since the average game of Go covers some 100 to 200 moves, if this
system were applied to chess an equivalent "byomi" standard would
be something like "5 moves in 10 minutes" and then increase the 
number of moves by 3 each period.  (Next: 8 moves in 10 minutes).

On the other hand, professional Go games are generally played over
many hours.  Sometimes each side recieves 7 or 8 hours of time.
In amateur tournaments, though, 60 or 90 minutes a side is the 
usual.

If anyone is interested, there are Go clocks which are able to keep
track of byomi time, and are programmable re: moves/length, and so
could function nicely as chess clocks.
 
 I think the idea for this kind of thing seeped into the chess world
 via someone who plays Go.
 
 C