import itertools,math
class Vector3:
    def __init__(self,x=0,y=0,z=0):
        self.x,self.y,self.z=x,y,z
    def __sub__(self,o):
        return Vector3(self.x-o.x,self.y-o.y,self.z-o.z)
    def outer_product(self,o):
        return Vector3(self.y*o.z-self.z*o.y,self.z*o.x-self.x*o.z,self.x*o.y-self.y*o.x)
    def inner_product(self,o):
        return self.x*o.x+self.y*o.y+self.z*o.z
    def norm(self):
        return math.sqrt(self.x**2+self.y**2+self.z**2)

def g():
    return Vector3(*map(float,raw_input().split()))

n=input()
P=g()
l=[g()-P for _ in range(n)]
ans=0
for a,b,c in itertools.combinations(l,3):
    t=(b-a).outer_product(c-a)
    ans+=abs(a.inner_product(t))/t.norm()
print(ans)