from time import time
start_time = time()

import sys
import io, os
input = sys.stdin.readline
#input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

import math
import random
random.seed(42)

m = 50
TIME_LIMIT = 0.85
L = 5*10**17

n =  int(input())
A = [0]*n
B = [0]*n
for i in range(n):
    a, b = map(int, input().split())
    A[i] = a
    B[i] = b

ans = []
for i in range(m):
    u, v = random.sample(range(n), 2)
    ans.append((u, v))

def calc_score(ans):
    Ac = A.copy()
    Bc = B.copy()
    for u, v in ans:
        x = (Ac[u]+Ac[v])//2
        Ac[u], Ac[v] = x, x
        y = (Bc[u]+Bc[v])//2
        Bc[u], Bc[v] = y, y
    v1 = abs(L-Ac[0])
    v2 = abs(L-Bc[0])
    cost = max(v1, v2)
    return cost

cost = calc_score(ans)
iter = 0
while True:
    iter += 1
    now_time = time()
    if now_time - start_time > TIME_LIMIT:
        break
    # ランダムに1操作を選んで変更する
    i = random.randint(0, m-1)
    u, v = random.sample(range(n), 2)
    pre = ans[i]
    ans[i] = (u, v)
    new_cost = calc_score(ans)
    if new_cost <= cost:
        cost = new_cost
    else:
        ans[i] = pre
print(len(ans))
for i in range(len(ans)):
    u, v = ans[i]
    u, v = u+1, v+1
    print(u, v)

if cost != 0:
    score = (int)(2000000-100000*math.log10(cost+1))
else:
    score = 2000050-len(ans)
print(cost, file=sys.stderr)
print(round(2000000-100000*math.log(cost+1)),  file=sys.stderr)
print(score, file=sys.stderr)