f(62)=f(61+1)
=f(61-1/2)+2
=f(60-1/2+1)+2
=f(60-1/2-1/2)+2+2
=f(59)+2+2
=f(62-n*3/2)+2*n
当n=41时
f(62)=f(1/2)+2*41=1+82=83