program sujet1_29_05_2012;
uses wincrt;
var p,q:integer;
ch:string;

procedure saisir;
begin
repeat
writeln('donner p entre 2 et 10 : ');readln(p);
until p in [2..10];
repeat
writeln('donner q entre 2 et 10 : ');readln(q);
until q in [2..10];
end;
function test(ch:string):boolean;
var i:integer;
begin
i:=0;
repeat
i:=i+1;
until not(ch[i]in['A'..'Z'])and(not (ch[i]in[' ','.']))or(i>length(ch)) ;
test:=i>length(ch);
end;

procedure lire;
begin
repeat
writeln('Donner un chaine : ');
readln(ch);
until test(ch);
end;

function coder(ch:string):string;
var j,i:integer;
begin
for i:=1 to length(ch) do
begin
if ch[i]in['A'..'Z'] then
                         begin
                         J:=ord(ch[i])-64;
                         ch[i]:=chr((p*j+q) mod 26 +1+64);
                         end;
end;
coder:=ch;
end;

begin
saisir;
lire;
writeln(coder(ch));
end.