Input Format
One line of input containing the space separated floating number values of the  and  coordinates of a point.
Output Format
Output the angle correct up to two decimal places.

### Problem solution in Python 3 programming language.

import math
class Points(object):
def __init__(self, x, y, z):
self.x=x
self.y=y
self.z=z
def __sub__(self, no):
return  Points((self.x-no.x),(self.y-no.y),(self.z-no.z))
def dot(self, no):
return (self.x*no.x)+(self.y*no.y)+(self.z*no.z)
def cross(self, no):
return Points((self.y*no.z-self.z*no.y),(self.z*no.x-self.x*no.z),
(self.x*no.y-self.y*no.x))

def absolute(self):
return pow((self.x ** 2 + self.y ** 2 + self.z ** 2), 0.5)
if __name__ == '__main__':
points = list()
for i in range(4):
a = list(map(float, input().split()))
points.append(a)
a, b, c, d = Points(*points[0]), Points(*points[1]),
Points(*points[2]), Points(*points[3])
x = (b - a).cross(c - b)
y = (c - b).cross(d - c)
angle = math.acos(x.dot(y) / (x.absolute() * y.absolute())
print("%.2f" % math.degrees(angle))

### Problem solution in Python 2 programming language.

import math

class Points(object):
def __init__(self, x, y, z):
self.x = x
self.y = y
self.z = z

def __sub__(self, no):
x = self.x - no.x
y = self.y - no.y
z = self.z - no.z
return Points(x, y, z)

def dot(self, no):
x = self.x * no.x
y = self.y * no.y
z = self.z * no.z
return x + y + z

def cross(self, no):
x = self.y * no.z - self.z * no.y
y = self.z * no.x - self.x * no.z
z = self.x * no.y - self.y * no.x
return Points(x, y, z)

def absolute(self):
return pow((self.x ** 2 + self.y ** 2 + self.z ** 2), 0.5)

points = list()
for i in range(4):
a = map(float, raw_input().split())
points.append(a)

A, B, C, D = Points(*points[0]), Points(*points[1]), Points(*points[2]), Points(*points[3])
X = (B - A).cross(C - B)
Y = (C - B).cross(D - C)
angle = math.acos(X.dot(Y) / (X.absolute() * Y.absolute()))

print "%.2f" % math.degrees(angle)