  We predict that the Josephson current in a clean s-wave superconductor-normal
metal-d-wave superconductor junction is periodic in superconducting phase
difference $\phi$ with period $\pi$ instead of $2\pi$. The frequency of
non-stationary Josephson effect is correspondingly $2\omega_J = 4eV.$ The
effect is due to coexistence in the normal layer of current carrying Andreev
levels with phase differences $\phi$ and $\phi+\pi.$
