import random
import math
from time import perf_counter
import sys

class TimeKeeper:
    def __init__(self):
        self.start_time = perf_counter()
    def is_time_over(self, LIMIT):
        return (perf_counter() - self.start_time) >= LIMIT
    def time_now(self):
        return (perf_counter() - self.start_time)

# 定数とグローバル変数
TARGET = 500000000000000000
N = 0
A = []
B = []
Order = []
BestOrder = []

def get_score():
    V1, V2 = A[0], B[0]
    for i in range(N - 1):
        V1 = (V1 + A[Order[i]]) // 2
        V2 = (V2 + B[Order[i]]) // 2
    return max(abs(TARGET - V1), abs(TARGET - V2))

def main():
    global N, A, B, Order, BestOrder
    tk = TimeKeeper()
    LIMIT = 0.85

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

    # 初期化
    Order = list(range(1, N))
    current_score = get_score()
    best_score = current_score
    
    # 焼きなまし
    loop = 0
    T0, T1 = 0.2, 0.2
    T = T0
    while True:
        loop += 1
        if loop % 1000 == 0:
            T = T0 + (T1 - T0) * tk.time_now() / LIMIT
            if tk.is_time_over(LIMIT):
                break

        idx1 = random.randrange(N - 1)
        idx2 = random.randrange(N - 1)
        Order[idx1], Order[idx2] = Order[idx2], Order[idx1]
        
        cand_score = get_score() # 変更候補
        diff = math.log10(current_score) - math.log10(cand_score) # diff > 0：改善
        
        if random.random() < math.exp(diff / T):
            # 採用
            if best_score > cand_score:
                best_score = cand_score
                BestOrder = Order[:]
            current_score = cand_score
        else:
            # 不採用の場合は元に戻す
            Order[idx1], Order[idx2] = Order[idx2], Order[idx1]
    
    ANS = [(1, BestOrder[i]+1) for i in range(N - 1)]

    print(len(ANS))
    for a in ANS:
        print(a[0], a[1])

    sc = int(2*10**6 - 10**5 * math.log10(best_score + 1))
    print(sc, best_score, loop, file=sys.stderr)

if __name__ == "__main__":
    main()