uses crt;
var a:char;
b:string;
begin b:='';
write('X:');
repeat a:=ReadKey;
if(a='0')or(a='1')then write(a);
case a of '0':b:='0'+b;
'1':b:=b+'1';
end;
until a=chr(13);
writeln;
write('result:',b);
readln;
end.