module Caesar;
const
	size = 25;

type
	Operation = (code,decode);

procedure C_D(s:string;k:integer;op: Operation): string;
var
	i,key: integer;
	resp: string;
	n,c: char;
begin
	resp := "";
	if op = Operation.decode then key := k else key := (26 - k) end;
	for i := 0 to len(s) - 1 do
		c := cap(s[i]);
		if (c >= 'A') & (c <= 'Z') then
			resp := resp +
				string(char(integer('A') + ((integer(c) - integer('A') + key )) mod 26));
		else
			resp := resp + string(c)
		end;
	end;
	return  resp
end C_D;

procedure {public} Cipher(s:string;k:integer):string;
var
	i: integer;
	resp: string;
	n,c: char;
begin
	return C_D(s,k,Operation.code)
end Cipher;

procedure {public} Decipher(s:string;k:integer):string;
var
	i: integer;
	resp: string;
	n,c: char;
begin
	return C_D(s,k,Operation.decode)
end Decipher;

var
	txt,cipher,decipher: string;

begin
	txt := "HI";cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
	writeln(txt," -c-> ",cipher," -d-> ",decipher);
	txt := "ZA";cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
	writeln(txt," -c-> ",cipher," -d-> ",decipher);
	txt := "The five boxing wizards jump quickly";
	cipher := Caesar.Cipher(txt,2);decipher := Caesar.Decipher(cipher,2);
	writeln(txt," -c-> ",cipher," -d-> ",decipher)
end Caesar.