Particle Number Dependence of The $N$-Body Simulations of Moon FormationThe formation of the Moon from the circumterrestrial disk has been investigated by using $N$-body simulations with the number $N$ of particles limited from $10^4$ to $10^5$. We develop an $N$-body simulation code on multiple Pezy-SC processors and deploy FDPS (Framework for Developing Particle Simulators) to deal with large number of particles. We execute several high- and extra-high-resolution $N
