A turn" of the head of a Turing machine means that the head changes its direction from moving to the right to moving to the left, or vice versa. For instance, the following sequence of moves of the head: R;R;R;R; S; S; S; S; L; L; L; constitutes one turn (where L=move to the left", R=move to the right", and S=\stay"). A Turing machine M is 1-turn if during any computation of M on any input word, the head of M makes at most one turn. What is the smallest class of languages that 1-turn Turing machines can accept? Prove your answer.