import math

def read_data():
    N = int(input())
    x, y, z = map(float, input().split())
    Ps = []
    for i in range(N):
        xi, yi, zi = map(float, input().split())
        Ps.append((xi-x, yi-y, zi-z))
    return N, Ps

def solve(N, Ps):
    dist, outer = preprocess(N, Ps)
    return sum(dist3(i, j, k, dist, outer, Ps) for i in range(N-2) for j in range(i+1, N-1) for k in range(j+1, N))


def preprocess(N, Ps):
    _sqrt = math.sqrt
    dist = [[_sqrt((xi-xj)**2+(yi-yj)**2+(zi-zj)**2) for xj, yj, zj in Ps] for xi, yi, zi in Ps]
    outer = [[(yi*zj - zi*yj, zi*xj - xi*zj, xi*yj - yi*xj) for xj, yj, zj in Ps] for xi, yi, zi in Ps]
    return dist, outer

def dist3(i, j, k, dist, outer, Ps):
    d1 = dist[i][j]
    d2 = dist[j][k]
    d3 = dist[k][i]
    s = (d1 + d2 + d3) / 2
    S = math.sqrt(s * (s - d1) * (s - d2) * (s - d3))
    xij, yij, zij = outer[i][j]
    xk, yk, zk = Ps[k]
    V = (xij * xk + yij * yk + zij * zk) / 2
    return abs(V)/S

N, Ps = read_data()
print(solve(N, Ps))