36分

b=0 a=float(input()) if a >= 0 and a < 5: b=-a+2.5 print('%.3f'%b) elif a >= 5 and a < 10: b=2-1.5*(a-3)*(a-3) print('%.3f'%a) else: b=a/3-1.5 print('%.3f'%b)