Program Zadacha;
uses crt;
const
buk = ['A'..'Z','a'..'z'];
var
i,j,q,k:integer;
s,s2:string;
ch:char;
a:set of char;
begin
clrscr;
writeln('Vvedite text:'); readln(s);
for i:=1 to length(s) do
if s[i] in buk then begin
ch:=s[i];
q:=0;
for j:=1 to length(s) do
if ch=s[j] then q:=q+1;
if q=1 then begin s2:=s2+ch; a:=a+[ch]; end;
end;
write(s2);
readkey;
end.