In a system two particles of masses $m_1=3 \mathrm{~kg}$ and $\mathrm{m}_2=2 \mathrm{~kg}$ are placed at certain distance from each other. The particle of mass $m_1$ is moved towards the center of mass of the system through a distance 2 cm . In order to keep the center of mass of the system at the original position, the particle of mass $\mathrm{m}_2$ should move towards the center of mass by the distance $\_\_\_\_$ cm.