<?php

    $text = 'Ukbn Txltbz nal hh Uoxelmgox wdvg Akw; hvu ogl rsm ar sbv ix jwz
mjotukj; mul nimo vaa prrf Qwkkb aak kau ww Ukpsf, ogq Kzpox vvl luf
yh Qsrjfa, hvu Ktp hzs lbn ph Kipsy; ttv Sdmehpfjsf tad igr
rcbkfgaplvj am uswrerwptk la hox cazkwn.  Agk wx wm fhpwln ds ztov
djoa mnwdl ers t wcjhxe au Crdjiy\'l vsxhkv, talfw ktf nppe.  Qnsdecqp
Qcjhxrnmdz nal avwfx, ncuknq cg whxlqy, bf wxsqgax tufutc cbk
cvfhgmwdz, ied mv fwqxvvf vhoo kpmn zauwlr, tur lc bafptm djst hl ltl
wcbuxxk mul tulaceg hs tig Cywfa; ttv fv lzrxjh lvhfe xjo mcal mu ltl
Rczs hx la apv pklgwbvr-cicmlgf, hgj ltvav wav qsax go ucko wd aakad swugbuu.
Sp hox iwzazv oy avw qanmcgr Ukbn Txltbz jam bdgb t febv op iflxt
bwgoxy, ghlz nhbjv ool fpsgan c qvokjuuo ff ysoes-vblpwrof ghmof, mul
k eizaogz vn iew zolwg jat wnngf oby wxiwn.
Djsu Txltbz jphrs, "At B ghpwgrv mvn cggsl eom kwkdteahg mo," uopw
rg, "W dhadp ztvei dvazx V wbkt pqf tr xwbhak; agk mgi vnn fptothhbt
yps hgultlz nimo fwztgioi tknsz, ttv ohv fbmhwf o yyahqn yh altj szk
cqal fksf mzfm Dhw."  Sbw ghf Mixi klgz la ztvei.  Hbv Yraoo vho ucu
yh Qsrjfa habew Roa the tict gjwja Gjfoci htk djcfvsff trga.  "P,
dqc, dbrd thdv tal ugcw gamg wrkqo ak hdvuzsxk hg ax," fajf Kkk.
"Xcm," hgyoqymu Krucf, "ttvrft wsnz pm hw rvz khxl hg tnyfjnl
Kthonx\'k nlpvsm, pb lvx sisut znojx, gfp apvn pl kaze gemn trgs aak
lgga mgdq aprt pl yfcp."  Fo Lci ggba mu ltl sztvosf ogq tp vho oshw-
mgzstx, szk zvtnybwr urasknq c tstmgz vn detk ofr t tomfex iciekl,
kpr h agfpmcc oy zywkxes, vrox yvpvn oqym srhpzwr vblmqpc qt txgl.
Djsu mnwk hbv tal qgzebpt cnn dsntt la kzznd avw axnd.  "Oqw," ccwk
Ucw, "pm ok fpuv fhy mgi mb gjxe wg af lzgdf."  "Spnhu," gsww Bwbkn,
"nq hoha hmf bf Ktp hzs mnlf vhkv wz aok pbm."  "Krnsm," kobq Kzpox,
"djcb txw aslvr, tur sfm n bfvtot hlerwd vn kaelg, sbw uatv sogb thxw
wcfcxrdaba khbuuk hann J; fo djcb mnwdlnfrx woq Ytv hju tkns."
"Lgupg zzkzmcf," jbclv Hjajp, "wsvv aak tqzb khta hzcn xnpyecv."  "W
gkzs wu ka," hvjwxysv Yraoo.
"S yoz mnw autp shu cx ar zoujeb cbk ygltlz, rnw P ksg xkcfgdspusr
kudpkofs, hvu mr kojwgt wbu votm nkksf.  P byonnvl harrf yac pc
ophlkvjuzm zn mos ockyd uqo wkuome xay uv, agk oxhxe I icd kevpxbwp
knz aak spcmetnysk hant xgro kb tr uoz jwlnmym, A sjhiqren omzxrx,
kpr zxz xayby th qcmfgry ujrywuo wkkqybj agk ragmnnu teqkcul.  Gfp hb
vgbnmn af jprnvlr lvtg I dcmo vc aak xmpzvsm codzxl io vho ycyej,
gjsyxof ilzv tklsk cy rqvcl qtcdmn; szk i iiolf jog ghsquqj hox
fczsxe, szk i gamo ksg ul tig ssfs vy zzq yqmek.  Hbv W yblmqwof hox
zcho ntlus uzd-whm, sbw poovixwsk fe babzeer hzgbz ghf tewcwuwkj am
djs ctrdqf cetbs hzs xieoknq; cbk tz ltl motklaahr bf b rlkkb P vgeq
dq o stxyq hvu lnzhjcnf Cbutvg, oa mnw rvwk oy dvaqa jat c tytflgz.
Kpr P tvhdvithxk hzs Vnsune, kpr aakjq P jvhxsr lkh lovvhc ywaa
igzshc ugytznz ooaf, xnci yidj o mkuffsmk oy ncdr ncoo jic jshw, gfp
mnok bt s shzdega cx mxylpy skvwu, ttv fomp htk ugzw plbupc wdvg
djspk ofeamgs.  Bu hzs anne qf ocqo hl ltlu nal hb ajhey cqw, cvfbgm
gkho mnw epvvwl vt lvx ftbi; axf hoxoj myzfwl oov ganfuu op vvl uufq
yh hox czmsm, rnw dsjs pvnhgd gkho iksovkb\'s ylolvxes; uje cjommy
kngv agv svtueg ossrl.  Nne vhoa vhw jssnmis pphz pendfu op icsw, gfp
gkho aodfz ww tal pgbx bf uje gjosx.  Gfp apvy plfw gabouknq vvlbx vmnovrl.
"Kpr h eolfsm nar mfga muen K sky o ttt az apv pkpaw cy yigg, wsvv
rkg ixgjp umnlr zvgfg, plbf ix c fvuk szk i dagazw cy lemnog uoabt;
kpr yhafp apv thw cx vbf mbptvg khl g tmul ff zvzv ztpe.  Pp hsu tlxz
ggfl lngqz ww vtywwutgee nekvvlk, lseameew im lkh ootuec qt nhrv.
Gjsu B ysi oqd, I plbl hhjasfs rka hgj kmsckew owe, ogq sveh gcg oby
mqiymkkk aprt al bg ghbnft roespokv yf oiexawfu muao je bghbktwp pb.
Kpr ox cwza ezta ts lcpnreu trg Qhlzdq.  Uwn talfw kxee oq dggzsxxk
sp hox Iseatv eqjshh muotg wrq klkk az vvv htsz.  Sbw ghfte S uod
pqiy-ttv-fdmetr koegxys, fobbqwkxxazn artbu ol o pvneqw.  Kpr aaok U
dgzs mnwq, Riz, tahh lvx yebut pcwy hl ltlu nal moafxe ticn djs
pcwyxyl yhqu tavi zolg ewgr lgvlej az apv Ilsofr hs Bsktkkb, hgj ltl
vgozm rghltp oy avwa pns nqro nccxrq foie Gplbzkrias, vho ywmx ux
Kthonx, otlv jhx ook oicebten nccxraqzb rt mos Gtyrrjpg, yp hox jsk
yh hox Tsfpdztr, vf sh mue ggacv cm Xgkflz.  Khxf fggx hp bv mi
mqapgm, szk azx hm hzsf gopm mi jcylk, szk lzvxzhwr fr og oy ktavnx;
kpr zbd gfomis mvcc ar nrnu, axf khlnwp apvm bu o nslfem wndkz aakq
ggfl ikjrlkklr ifauag.  Aof trg hobxv epf jpklov qebtiu uzqb aak';



    $r = (isset($_REQUEST['r']) ? (int) $_REQUEST['r'] : 0) % 26;

    $l = strlen($text);

    $a = array(10, 2, 14, 7, 19, 6, 18, 12, 7, 8, 17, 0, 19, 7, 14, 18, 14, 19, 13, 0, 1, 2, 0);
    $p = count($a);

    $x = 0;
    for($i = 0; $i < $l; $i++) {
        $o = ord($text[$i]);
        $s = $o - $a[($i - $x) % $p];
        if($o >= 97 && $o <= 122) {
            $text[$i] = chr($s > 122 ? ($s % 122 + 96) : ($s < 97 ? (122 + ($s - 96)) : $s));
        } elseif($o >= 65 && $o <= 90) {
            $text[$i] = chr($s > 90 ? ($s % 90 + 64) : ($s < 65 ? (90 + ($s - 64)) : $s));
        } elseif($o < 32) {
            $x = $i + 1;
        } else {
            $x++;
        }
    }

    echo '<a href="?r=', ($r + 1) % 26, '">Next</a>';
    for($i = 0; $i < $l; $i++) {
        $o = ord($text[$i]);
        if($o < 97 || $o > 122) continue;
        $s = $o + $r;
        $text[$i] = chr($s > 122 ? ($s % 122 + 96) : $s);
    }

    $q = array('1:29', '6:46',
    'the product of the first two primes', '2:37', '14:41', '17:3', '27:40',
    'the first prime', '2:33', '1:1', '7:45', '17:29', '21:31', '12:17',
    'the product of the first two primes', '22:42', '15:18', '24:33', '27:46', '12:29', '25:66', '7:47');

    echo '<pre>';
    $ta = explode("\n", $text);
    foreach($q as $qr) {
        $qa = explode(':', $qr);
        if(count($qa) == 2) {
            $a = (int) $qa[0];
            $b = (int) $qa[1];
            $te = preg_replace('/([^a-zA-Z0-9]*)/', '', $ta[$a]);
            echo $te[$b], "\n";
        } else {
            echo '<u>', $qr, "</u>\n";
        }
    }
    echo '</pre>';

    echo '<pre>', $text, '</pre>';