At time t=0, a disk of radius 1 m starts to roll without slipping on a horizontal plane with angular acceleration α=2/3 rad s⁻². A small stone is stuck at the initial contact point. At t=√π s it detaches and flies off tangentially. The maximum height measured from the plane is 1/2+x/10 m. The value of x is _____. Take g=10 m s⁻².