  The presence of a population of a large number ($\sim$400) of almost coeval
(100--300 Myr) super star clusters (SSCs) in the disk of M82 offers an
opportunity to construct the Cluster Initial Mass Function (CIMF) from the
observed present-day Cluster Mass Function (CMF). We carry out the dynamical
and photometric evolution of the CMF assuming the clusters move in circular
orbits under the gravitational potential of the host galaxy using the
semi-analytical simulation code EMACSS. We explore power-law and log-normal
functions for the CIMFs, and populate the clusters in the disk assuming
uniform, power-law, and exponential radial distribution functions. We find that
the observed CMF is best produced by a CIMF that is power-law in form with an
index of 1.8, for a power-law radial distribution function. More importantly,
we establish that the observed turn-over in the present-day CMF is the result
of observational incompleteness rather than due to dynamically induced effects,
or an intrinsically log-normal CIMF, as was proposed for the fossil starburst
region B of this galaxy. Our simulations naturally reproduce the mass-radius
relation observed for a sub-sample of M82 SSCs.
