#!/usr/bin/env python3
"""Harmonic spring: E = 0.5 * k * (r - r0)^2, k=1.0, r0=1.0."""
import math

lines = open("from_eon_to_extpot").readlines()
# Skip 3 box lines
atoms = []
for l in lines[3:]:
    tok = l.split()
    atoms.append((int(tok[0]), float(tok[1]), float(tok[2]), float(tok[3])))

N = len(atoms)
forces = [[0.0, 0.0, 0.0] for _ in range(N)]
energy = 0.0
k = 1.0
r0 = 1.0

for i in range(N):
    for j in range(i + 1, N):
        dx = atoms[j][1] - atoms[i][1]
        dy = atoms[j][2] - atoms[i][2]
        dz = atoms[j][3] - atoms[i][3]
        r = math.sqrt(dx * dx + dy * dy + dz * dz)
        if r < 1e-12:
            continue
        energy += 0.5 * k * (r - r0) ** 2
        fmag = k * (r - r0) / r
        forces[i][0] += fmag * dx
        forces[i][1] += fmag * dy
        forces[i][2] += fmag * dz
        forces[j][0] -= fmag * dx
        forces[j][1] -= fmag * dy
        forces[j][2] -= fmag * dz

with open("from_extpot_to_eon", "w") as f:
    f.write(f"{energy:.15f}\n")
    for fx, fy, fz in forces:
        f.write(f"{fx:.15f} {fy:.15f} {fz:.15f}\n")
