Constant curve25519_dalek::constants::BASEPOINT_ORDER_MINUS_1

pub const BASEPOINT_ORDER_MINUS_1: Scalar = Scalar{bytes:
           [236, 211, 245, 92, 26, 99, 18, 88, 214, 156, 247, 162, 222, 249,
            222, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16],}

BASEPOINT_ORDER_MINUS_1 is the order of base point minus one, i.e. l-1, in little-endian bytes.