import io, os
input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

# 行基本変形（floatで計算）
def row_transformation(A,x): # xは正方行列の行数
    for i in range(x):  
        for j in range(x):
            if i==j:
                continue

            base=A[i][i]
            target=A[j][i]
            if target==0:
                continue

            for k in range(x):
                    A[j][k]-=A[i][k]*(target/base)

    return A

# 逆行列を掃き出し法で計算（floatで計算）
def inv_transformation(A,x): # xは正方行列の行数
    for i in range(x):
        A[i]+=[0]*x
        A[i][i+x]=1
    
    for i in range(x):  
        for j in range(x):
            if i==j:
                continue

            base=A[i][i]
            if base!=1:
                for k in range(x*2):
                    A[i][k]/=base
                    
            target=A[j][i]
            if target==0:
                continue

            for k in range(x*2):
                    A[j][k]-=A[i][k]*target

    B=[[0]*x for i in range(x)]

    for i in range(x):
        for j in range(x):
            B[i][j]=A[i][j+x]

    return B
    
def prod(A,B,k,l,m):# A:k*l,B:l*m
    C=[[None for i in range(m)] for j in range(k)]

    for i in range(k):
        for j in range(m):
            ANS=0
            for pl in range(l):
                ANS=(ANS+A[i][pl]*B[pl][j])

            C[i][j]=ANS

    return C       

N=int(input())
x,y,z=map(float,input().split())
P=[tuple(map(float,input().split())) for i in range(N)]

ANS=0

for i in range(N):
    for j in range(i+1,N):
        for k in range(j+1,N):
            x0,y0,z0=P[i]
            x1,y1,z1=P[j]
            x2,y2,z2=P[k]

            A=[[x0,y0,1],[x1,y1,1],[x2,y2,1]]

            INV=inv_transformation(A,3)

            X=prod(INV,[[z0],[z1],[z2]],3,3,1)
            a=X[0][0]
            b=X[1][0]
            c=X[2][0]

            ANS+=abs(a*x+b*y-z+c)/((a*a+b*b+1)**(1/2))

print(ANS)