def equation(x):

   if 1 < x <= 20:

       y = (5.34+x**2)/(1+x)

   elif x <= 1:

       y = 7.5 * x**2 - 1.7 * x**2

   elif x > 20:

       q = 4.2

       y = 1 + x**3 + q

   return y

print(equation(float(input())))