  The first hint of the leptonic CP phase $\delta_{CP}=-90^\circ$ has already
came from the long-baseline neutrino oscillation experiment T2K. This hint is
derived from the neutrino data of T2K and currently it is running in the
antineutrino mode. In this work we ask the question what should be the
proportion of neutrino and antineutrino running of the T2K experiment to
discover CP violation in the leptonic sector.
