#ver4
#一番答えが大きくなるものを選ぶ(貪欲)
#(i,j)を辞書順に調べる
#解を変える適当焼きなまし
import time
t0=time.time()
import random
random.seed(14)
N=int(input())
A=[]
B=[]
cons=5*10**17
for _ in range(N):
    a,b=map(int,input().split())
    A.append(a)
    B.append(b)
A_base=[a for a in A]
B_base=[b for b in B]
op_cnt=0
#costは低ければ低いほどよい
def calculate_cost(a,b):
    return max(abs(a-cons),abs(b-cons))

def op(u,v):
    global A
    global B
    a,b=A[u],A[v]
    c,d=B[u],B[v]
    A[u],A[v]=(a+b)//2,(a+b)//2
    B[u],B[v]=(c+d)//2,(c+d)//2
    
cost=calculate_cost(A[0],B[0])
ans=[]
while op_cnt<50:
    u=-1
    v=-1
    best_cost=cost
    for i in range(N):
        for j in range(i+1,N):
            if(i==0):
                new_cost=calculate_cost((A[i]+A[j])//2,(B[i]+B[j])//2)
            if(new_cost<best_cost):
                u=i
                v=j
                best_cost=new_cost
        if(v!=-1):
            break
    if(v==-1):
        break
    else:
        op_cnt+=1
        op(u,v)
        ans.append([u,v])
        cost=calculate_cost(A[0],B[0])
while op_cnt<50:
    (u,v)=ans[-1]
    ans.append([u,v])
    op_cnt+=1
def calculate_cost_by_ans(ans):
    X=len(ans)
    cal_A=[a for a in A_base]
    cal_B=[b for b in B_base]
    for i in range(X):
        (u,v)=ans[i]
        a,b=cal_A[u],cal_A[v]
        c,d=cal_B[u],cal_B[v]
        cal_A[u],cal_A[v]=(a+b)//2,(a+b)//2
        cal_B[u],cal_B[v]=(c+d)//2,(c+d)//2
    # print(cal_A[0],cal_B[0])
    return calculate_cost(cal_A[0],cal_B[0])
# print(cost)
# print(A[0],B[0])
# print(calculate_cost_by_ans(ans),"?")
i=0
while time.time()-t0<0.95:
    i=(i+1)%op_cnt
    (u,v)=ans[i]
    new_u=random.randint(0,N-1)
    new_v=random.randint(0,N-2)
    if(new_v==new_u):
        new_v+=1
    # print(u,v)
    # print(new_u,new_v,"new")
    ans[i]=[new_u,new_v]
    new_cost=calculate_cost_by_ans(ans)
    # print(cost,"cost")
    # print(new_cost,"new_cost")
    if((time.time()-t0)*(new_cost-cost)/10**(15.0-15.0*(time.time()-t0)) > random.random()):
    # if(cost<new_cost):
        ans[i]=[u,v]
    else:
        # if(cost!=new_cost):
        #     print(cost,new_cost)
        cost=new_cost
    
# print(cost)
print(len(ans))
for (u,v) in ans:
    print(u+1,v+1)