#ver2
#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
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)
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,(c+d)//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(N):
            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])
# print(cost)
print(len(ans))
for (u,v) in ans:
    print(u+1,v+1)