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 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.
