A clock is made out of a disk of radius R=10 cm which is hung by a

A clock is made out of a disk of radius R=10 cm which is hung by a point on its edge and oscillates. All of a sudden, a circular part right next to the hanging point of radius R/2 falls off, but the clock continues oscillating. What is the absolute value of the difference in s between the periods of oscillation before and after the part fell off?