from time import time
st=time()

import sys
input = lambda: sys.stdin.readline().rstrip()
from math import log10
from copy import copy,deepcopy
from random import randint,random,choice
from bisect import bisect,bisect_left,insort

MAX_OP=50
TIME_LIMIT=0.9
TARGET_NUM=5*10**17

# カード1のスコアだけ見ればいいのか
# 奇数回目の操作でカード1以外を操作する
# 偶数回目でカード1を操作する

# カード1のスコアを計算

def calc_front():return abs(tempAB[0][0]-TARGET_NUM)

def calc_back():return abs(tempAB[0][1]-TARGET_NUM)

def calc_Score(cnt):
    V1=calc_front()
    V2=calc_front()
    
    temp=max(V1,V2)

    if temp==0:return 2000050-cnt
    return int(2000000-100000*log10(temp+1))

def rewrite(u,v):
    tempf=(tempAB[u][0]+tempAB[v][0])//2
    tempAB[u][0]=tempf
    tempAB[v][0]=tempf

    tempb=(tempAB[u][1]+tempAB[v][1])//2
    tempAB[u][1]=tempb
    tempAB[v][1]=tempb



def Judge(N,AB,X,UV):
    def WrongAnswer(str):
        print("Wrong Answer (" + str + ")")
        exit(0)

    # Step 1. テストケースの入力を受け取る

    A = [0] * (N + 1)
    B = [0] * (N + 1)
    for i in range(1, N+1):
        A[i], B[i] = AB[i-1]

    # Step 2. あなたの出力を受け取る
    if X < 0 or X > 50:
        WrongAnswer("X is out of range")

    U = [0] * (X + 1)
    V = [0] * (X + 1)
    for i in range(1, X+1):
        U[i], V[i] = UV[i-1]
        if U[i] == V[i]:
            WrongAnswer("U[i] and V[i] are same")
        elif U[i] < 1 or U[i] > N:
            WrongAnswer("U[i] is out of range")
        elif V[i] < 1 or V[i] > N:
            WrongAnswer("V[i] is out of range")

    # Step 3. シミュレーションを行う
    for i in range(1, X+1):
        avgA = (A[U[i]] + A[V[i]]) // 2
        avgB = (B[U[i]] + B[V[i]]) // 2
        A[U[i]] = avgA
        A[V[i]] = avgA
        B[U[i]] = avgB
        B[V[i]] = avgB

    # Step 4. 出力
    ErrorA = abs(500000000000000000 - A[1])
    ErrorB = abs(500000000000000000 - B[1])
    Score = (int)(2000000.0 - 100000.0 * log10(1.0 * max(ErrorA, ErrorB) + 1.0))
    if ErrorA == 0 and ErrorB == 0:
        Score = 2000050 - X
    print("Accepted!")
    print("Error of A[1] = " + str(ErrorA))
    print("Error of B[1] = " + str(ErrorB))
    print("Score = " + str(Score))


N=int(input())
AB=[list(map(int, input().split()))  for _ in range(N)]


NowScore=0
UV=[]
premove=-1
preop=-1

while time()-st<=TIME_LIMIT:

    tempAB=deepcopy(AB)    
    tempUV=[]
    pretempScore=0
    opcnt=randint(0,MAX_OP)

    for cnt in range(1,opcnt+1):

        # 各カード表裏について値を記録する
        F_set=[]
        B_set=[]

        for i in range(1,N):

            a,b=tempAB[i]
            insort(F_set,(a,i))
            insort(B_set,(b,i))

        if cnt&1:

            F,B=tempAB[0]

            # 表裏を適当に書き換える
            k=randint(0,1)
            preop=k
            if k:
                while 1:
                    a,u=choice(F_set)
                    t=calc_front()
                    bk=bisect_left(F_set,(2*t-a,0))
                    if bk>=N-1:bk=N-2

                    b,v=F_set[bk]
                    if u!=v:break
                
                rewrite(u,v)


            else:
                while 1:
                    c,u=choice(B_set)
                    t=calc_back()
                    dk=bisect_left(B_set,(2*t-c,0))
                    if dk>=N-1:dk=N-2

                    d,v=B_set[dk]
                    if u!=v:break

                rewrite(u,v)

            tempUV.append((u+1,v+1))


        else:
            k=randint(0,1)

            if k:

                a=tempAB[0][0]
                bk=bisect_left(F_set,(2*TARGET_NUM-a,0))
                if bk>=N-1:bk=N-2

                b,v=F_set[bk]
                rewrite(0,v)
            else:

                c=tempAB[0][1]
                dk=bisect_left(B_set,(2*TARGET_NUM-c,0))
                if dk>=N-1:dk=N-2

                d,v=B_set[dk]

                rewrite(0,v)

            tempUV.append((1,v+1))


    tempScore=calc_Score(cnt)
    if tempScore>NowScore:
        NowScore=tempScore
        UV=deepcopy(tempUV)


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

Judge(N,AB,len(UV),UV)