def score(a, b):
    return max(abs(a-5*10**17), abs(b-5*10**17))

import time
import random
import sys
input = sys.stdin.readline
N = int(input())
AB = [list(map(int, input().split())) for _ in range(N)]
st_time = time.time()
A = []
B = []
for a, b in AB:
    A.append(a)
    B.append(b)
min_ans = []
ini_sco = min_sco = score(A[0], B[0])
while time.time()-st_time<0.9:
    AA = A[:]
    BB = B[:]
    ans = []
    for i in range(50):
        if i%5==0:
            u = v = 0
        else:
            u = v = random.randrange(N)
        while u==v:
            v = random.randrange(N)
        AA[u] = AA[v] = (AA[u]+AA[v])//2
        BB[u] = BB[v] = (BB[u]+BB[v])//2
        ans.append((u+1, v+1))
        if u==0 or v==0:
            sco = score(AA[0], BB[0])
            if sco<min_sco:
                min_sco = sco
                min_ans = ans[:]
                print(sco, file=sys.stderr)
print(len(min_ans))
for a in min_ans:
    print(*a)