  We show how the dense shells of circumstellar gas immediately outside the red
supergiants (RSGs) can affect the early optical light curves of Type II-P SNe
taking the example of SN 2013ej. The peak in V, R and I bands, decline rate
after peak and plateau length are found to be strongly influenced by the dense
CSM formed due to enhanced mass loss during the oxygen and silicon burning
stage of the progenitor. We find that the required explosion energy for the
progenitors with CSM is reduced by almost a factor of 2.
