use strict;

my $probe = $ARGV[0];
print "probing for $probe\n";
our @probes = split //,$probe;

undef $/;
our $data = lc <DATA> . "jkwy" x 10;
$data =~ s/(\015|\012)+/ /g; # Needed to solve newline mismatches
our @letter = split //, $data;

sub poleval {
    my ($x, $r) = (shift, 0);
    $r = ( $r * $x + $_ ) % 683 for @_;
    $r;
}

sub get_letter {
   my $val = shift;
   return grep { $letter[$_] eq $val } 0..$#letter;
}

my @p0 = get_letter($probes[0]);
my @p1 = get_letter($probes[1]);
my @p2 = get_letter($probes[2]);
my @p3 = get_letter($probes[3]);
my @p4 = get_letter($probes[4]);
my $p5 = $probes[5];
my $total = scalar(@p0)*scalar(@p1)*scalar(@p2)
            *scalar(@p3)*scalar(@p4);
print "Estimated $total count\n";

my $count = $#letter;
my $comb = 0;
my ($a, $b, $c, $d, $e, $r, $x, $y, $z, $q, $ap, $bp, $cp);
my ($app, $bpp);
my ($x0, $x1, $x2, $x3, $x4, $x5, $x6, $x7, $x8, $x9);
for $a (@p0) {
   for $b (@p1) {
      for $c (@p2) {
        $ap = ($c - $a) - 2*($b - $a);
        for $d (@p3) {
        $bp = ($d - $a) - 3*($b - $a);
        for $e (@p4) {
            $cp = ($e - $a) - 4*($b - $a);
            $app = ($bp - 3*$ap);
            $bpp = ($cp - 6*$ap);
            # 370 is the inverse of 24 mod 683.
            $r = (370*($bpp - 4*$app)) % 683;
            # 114 is the inverse of 6 mod 683.
            $x = (114*($app - 36*$r)) % 683;
            # 342 is the inverse of 2 mod 683.
            $y = (342*($ap - 14*$r - 6*$x)) % 683;
            $z = ($b - $a - $r - $x - $y) % 683;
            $x5 = poleval(5,$r,$x,$y,$z,$a);
            next if $x5 > $count;
            next if ($letter[$x5] ne $p5);
            $x6 = poleval(6,$r,$x,$y,$z,$a);
            next if $x6 > $count;
            $x7 = poleval(7,$r,$x,$y,$z,$a);
            next if $x7 > $count;
            $x8 = poleval(8,$r,$x,$y,$z,$a);
            next if $x8 > $count;
            $x9 = poleval(9,$r,$x,$y,$z,$a);
            next if $x9 > $count;
            print "possible at $r, $x, $y, $z, $a: ";
            print $probes[0],$probes[1],$probes[2],$probes[3];
            print $probes[4],$letter[$x5],$letter[$x6],$letter[$x7];
            print $letter[$x8],$letter[$x9],"\n";
         }
       }
      }
   }
}

__DATA__
Lupus et agnus
Ad rivum eundem lupus et agnus venerant,
siti compulsi. Superior stabat lupus,
longeque inferior agnus. Tunc fauce improba
latro incitatus iurgii causam intulit;
'Cur' inquit 'turbulentam fecisti mihi
aquam bibenti?' Laniger contra timens
'Qui possum, quaeso, facere quod quereris, lupe?
A te decurrit ad meos haustus liquor'.
Repulsus ille veritatis viribus
'Ante hos sex menses male' ait 'dixisti mihi'.
Respondit agnus 'Equidem natus non eram'.
'Pater hercle tuus' ille inquit 'male dixit mihi';
atque ita correptum lacerat iniusta nece.
Haec propter illos scripta est homines fabula
qui fictis causis innocentes opprimunt.
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