@staticmethod
def d():
    (n, *ab) = map(int, sys.stdin.read().split())
    c = np.array(ab).reshape(2, n, 2)
    g = c.mean(axis=1)
    d = np.sqrt(((c - g[:, None, :]) ** 2).sum(axis=(- 1))).sum(axis=1)
    print((d[1] / d[0]))
@staticmethod
def d():
    (n, *ab) = map(int, sys.stdin.read().split())
    c = np.array(ab).reshape(2, n, 2)
    g = c.mean(axis=1)
    d = np.sqrt(((c - g[:, None, :]) ** 2).sum(axis=(- 1))).sum(axis=1)
    print((d[1] / d[0]))