from dataclasses import dataclass, field
# from sortedcontainers import SortedList, SortedDict, SortedSet
from random import random, seed, randrange, choice, sample
# from itertools import permutations, combinations, product
from collections import deque, defaultdict, Counter
# from heapq import heapify, heappush, heappop
# from bisect import bisect_right, bisect_left
from time import time
import sys
sys.setrecursionlimit(1000000)
seed(0)

def input():
    return sys.stdin.buffer.readline().rstrip().decode(encoding='utf-8')
try:    isLocal
except: isLocal = False
if isLocal: input = line

def randrange_s(stop:int)->int: return int(random()*stop)
def randrange_ss(start:int, stop:int)->int: return int(random()*(stop-start)+start)

class AHC():
    def __init__(self):
        self.sTime = time()
        self.get_input()
        self.preprocessing()

    def get_input(self):
        self.N = int(input())
        AB = [list(map(int, input().split())) for _ in range(self.N)]
        self.A, self.B = [], []
        for a, b in AB:
            self.A.append(float(a))
            self.B.append(float(b))
        return

    def preprocessing(self):
        self.target = float(5*10**17)
        return 

    def get_score(self):
        return max(abs(self.target-self.A[0]), abs(self.target-self.B[0]))

    def get_score2(self, a, b):
        return max(abs(self.target-a), abs(self.target-b))

    def greedy(self):
        self.ans = []
        self.hist = set()
        self.cur = self.get_score()
        self.cnt = 0
        self.eTime = self.sTime+0.9
        while self.cnt<50 and time()<self.eTime:
            while self.cnt<50 and time()<self.eTime:
                # カード1と作用させる
                evaList = []
                for i in range(1, self.N):
                    a = (self.A[0]+self.A[i])/2
                    b = (self.B[0]+self.B[i])/2
                    evaList.append([self.get_score2(a, b), i])
                nxt, v = min(evaList)
                if nxt>=self.cur: break
                self.hist = set()
                self.cnt += 1
                self.cur = nxt
                self.ans.append(f"1 {v+1}")
                mean = (self.A[0]+self.A[v])/2
                self.A[0] = mean
                self.A[v] = mean
                mean = (self.B[0]+self.B[v])/2
                self.B[0] = mean
                self.B[v] = mean

            if self.cnt<49 and time()<self.eTime:
                # カード1を理想の状態にするためのカード作り
                target_A = self.target-self.A[0]+self.target
                target_B = self.target-self.B[0]+self.target
                evaList = []
                for u in range(1, self.N-1):
                    for v in range(u+1, self.N):
                        if (u, v) in self.hist: continue
                        a = (self.A[u]+self.A[v])/2
                        b = (self.B[u]+self.B[v])/2
                        evaList.append([(target_A-a)**2+(target_B-b)**2, u, v])
                if len(evaList)==0: break
                _, u, v = min(evaList)
                self.cnt += 1
                self.ans.append(f"{u+1} {v+1}")
                self.hist.add((u, v))
                mean = (self.A[u]+self.A[v])/2
                self.A[u] = mean
                self.A[v] = mean
                mean = (self.B[u]+self.B[v])/2
                self.B[u] = mean
                self.B[v] = mean
        return

    def output(self):
        print(len(self.ans))
        if len(self.ans)>0:
            print("\n".join(self.ans))

ahc = AHC()
ahc.greedy()
ahc.output()