from time import time
start = time()
import sys
from random import randint
from itertools import combinations
def input(): return sys.stdin.readline().rstrip()
def ii(): return int(input())
def ms(): return map(int, input().split())
def li(): return list(map(int,input().split()))
# ////////////////////////////////
N = ii()
A = list()
B = list()
for i in range(N):
  a,b = ms()
  A.append([a,i])
  B.append([b,i])
NUM = [i for i in range(2,N)]
STAND = 5*pow(10,17)

def create_abs(A,B,V1,V2):
  ABS = list()
  for v in range(1,N):
    na,nb = (A[0][0]+A[v][0])//2,(B[0][0]+B[v][0])//2
    n1,n2 = abs(na-STAND),abs(nb-STAND)
    tmp = max(V1,V2)-max(n1,n2)
    ABS.append((tmp,v))
  ABS.sort(reverse=True)
  return ABS

def other_merge(A,B): # STANDにできるだけ近いやつを作る
  CAND = list()
  for (u,v) in combinations(NUM,2):
    na,nb = (A[u][0]+A[v][0])//2,(B[u][0]+B[v][0])//2
    n1,n2 = abs(na-STAND),abs(nb-STAND)
    CAND.append((max(n1,n2),u,v))
  CAND.sort()
  ind = randint(0,2)
  u,v = CAND[ind][1],CAND[ind][2]
  return u,v

def play(A,B):
  global MAXV,BEST_ANS
  TURN = 0
  ANS = list()
  V1,V2 = abs(A[0][0]-STAND),abs(B[0][0]-STAND)
  while TURN<50:
    if time()-start>2.85: return
    ABS = create_abs(A,B,V1,V2)
    if ABS[0][0]==0: # 頭打ちになったら1以外とマージする
      u,v = other_merge(A,B)
    else:
      u,v = 0,ABS[0][1]
    ANS.append((u+1,v+1))
    na,nb = (A[u][0]+A[v][0])//2,(B[u][0]+B[v][0])//2
    if u==0:
      n1,n2 = abs(na-STAND),abs(nb-STAND)
      V1,V2 = n1,n2
    A[u][0],A[v][0],B[u][0],B[v][0] = na,na,nb,nb
    TURN += 1
    
  if MAXV>max(V1,V2):
    MAXV = max(V1,V2)
    BEST_ANS = [a[:] for a in ANS]
    return

BEST_ANS = list()
MAXV = pow(10,18)

while time()-start<0.85:
  AA = [a[:] for a in A]
  BB = [b[:] for b in B]
  play(AA,BB)

print(len(BEST_ANS))
for u,v in BEST_ANS: print(u,v)