somente numeros da string

var s1, s2: string;
    i: Integer;
begin
  s1 := ´01256252LH21O´;
  s2 := ´´;
  for i := 1 to Length(s1) do
    if s1[i] in [´0´..´9´] then
      s2 := s2 + s1[i];
  ShowMessage(s2);
end;

function SomenteNumeros(AString: string): string;
var
  i : Integer;
begin
  Result := ´´;
  for i := 1 to Length(AString) do
    if AString[i] in [´0´..´9´] then
      Result := Result + AString[i];
end;