program Project1;
var mes, mesK: string;
    i: integer;
begin
Readln (mes);
 
    for i := 1 to length(mes) do
     begin
          if mes[i] = mes[i+1] then
           mesK := ''
          Else
           mesK := mes[i];
    Write (mesk);
    End;
Readln;
end.