#! perl -slw
use strict;
#use Math::Random::MT qw[ rand ];

$|++;

our $I //= 1e6;

my( $tried, $good );

for ( 1 .. $I ) {
    ++$tried;
    my @b = map int( rand 6 ), 1 .. 64;
    $good += checkBoard( \@b );
#    displayBoard( \@b ); print "$good of $tried"; <STDIN>;
    printf "\r%10u %18.15f ", $tried, $good / $tried unless $tried % 10000;
}


sub checkBoard {
    my $ref = shift;
    for(
        [0..7],[8..15],[16..23],[24..31],[32..39],[40..47],[48..55],[56..63],
        [ 0, 8,16,24,32,40,48,56],
        [ 1, 9,17,25,33,41,49,57],
        [ 2,10,18,26,34,42,50,58],
        [ 3,11,19,27,35,43,51,59],
        [ 4,12,20,28,36,44,52,60],
        [ 5,13,21,29,37,45,53,61],
        [ 6,14,22,30,38,46,54,62],
        [ 7,15,23,31,39,47,55,63],
    ) {
        my $n = 0;
        join( '', @{$ref}[ @$_ ] ) =~ m[(.)\1\1] and return 0;
    }
    return 1
}
sub displayBoard {
    print for unpack '(A16)*', join ' ', @{ $_[ 0 ] }
}