a = 0
b = 1
n = int(input())

def f(x):
  return (x**3 + n ** 3)**0.5

def Simpson(f,a,b,m):
    df = (b-a)/(2*m)
    h = (b-a)/(2*m)
    sum = 0
    for i in range(1,m+1):
        x1 = a + df*(2*i -2)
        x2 = a + df*(2*i -1)
        x3 = a + df*(2*i)
        f1 = f(x1)
        f2 = f(x2)
        f3 = f(x3)
        sum += h*(f1 + 4*f2 + f3)/3
    return sum

# 結果の表示
print(Simpson(f,a,b,10 ** 6))