import sys import time import random from heapq import heapify, heappush, heappop input = lambda: sys.stdin.readline().rstrip() # ----------------------- # n, m = map(int, input().split()) ab = [tuple(map(int, input().split())) for _ in range(n)] ab_set = set(ab) ALP = 5 ALP2 = 25 LIMIT = 0.85 START = time.time() def calc_score(root): ans = 0 E = [] for i in range(1, n): u, v = root[i][1]-1, root[i-1][1]-1 tmp = (ab[u][0] - ab[v][0])*(ab[u][0] - ab[v][0]) + (ab[u][1] - ab[v][1])*(ab[u][1] - ab[v][1]) heappush(E, (tmp, i)) if len(E) > 8: heappop(E) ans += ALP2 * tmp v = root[-1][1] tmp = (ab[0][0] - ab[v][0])*(ab[0][0] - ab[v][0]) + (ab[0][1] - ab[v][1])*(ab[0][1] - ab[v][1]) ans += ALP2 * tmp heappush(E, (tmp, n)) if len(E) > 8: heappop(E) stations = [] E.sort(key=lambda x: x[1]) for c,i in E: if i == n: v = root[-1][1]-1 stations.append(((ab[0][0] + ab[v][0])>>1, (ab[0][1] + ab[v][1])>>1)) ans -= c * ALP2 ans += c * ALP else: u, v = root[i][1]-1, root[i-1][1]-1 stations.append(((ab[u][0] + ab[v][0])>>1, (ab[u][1] + ab[v][1])>>1)) ans -= c * ALP2 ans += c * ALP for i in range(8): if E[i][1] + i > len(root): root.append((E[i][1]+i, (2, i+1, 0))) else: root.insert(E[i][1]+i, (2, i+1, 0)) return root, stations, ans def make_stations(): stations = [] return stations def make_root(): C = [(1, i, ab[i-1]) for i in range(2, n+1)] c = [] d = random.randint(80, 600) a, b = list(range(1000//d + 3)), list(range(1000//d + 3)) i = random.randint(0, len(a)) a = a[i:] + a[:i] b = b[i:] + b[:i] for i in a: for j in b: tmp = [] for k in C: if d*i <= k[2][0] <= d*(i+1) and d*j <= k[2][1] <= d*(j+1): tmp.append(k) for t in tmp: C.remove(t) tmp.sort(key=lambda x: x[2]) c.extend(tmp) return [(1, 1, 0)] + c vestscore = float('inf') st, ro = [], [] while time.time() - START < LIMIT: root = make_root() try: root, stations, score = calc_score(root) if score < vestscore: vestscore = score st = stations[:] ro = root[:] except IndexError: pass for i,j in st: print(i, j) print(len(ro)+1) for i,j,_ in ro: print(i, j) print(1, 1)