#include <bits/stdc++.h>
using namespace std;
using ll=long long;
struct card{
    ll a,b;
    card(){}
    card(ll a,ll b):a(a),b(b){}

    void print(){
        cout<<a<<" "<<b<<endl;
    }
};
bool operator<(card x,card y){
    if(x.a==y.a)return x.b<y.b;
    else return x.a<y.a;
}
card operator+(card x,card y){
    return card((x.a+y.a)/2,(x.b+y.b)/2);
}
const int m=6;
const vector<int> v={25,13,6,3,2,1};
const ll x=500000000000000000;
int main(){
    int n;
    cin>>n;
    vector<card> c(n);
    random_device seed;
    mt19937 rnd(seed());
    for(int i=0;i<n;i++){
        ll a,b;
        cin>>a>>b;
        c[i]=card(a,b);
    }
    cout<<50<<endl;

    auto f=[&](int p){
        card t=c[p]+c[(p+1)%n];
        int index=(p+1)%n;
        for(int j=2;j<n;j++){
            card tt=c[p]+c[(p+j)%n];
            if(max(abs(t.a-x),abs(t.b-x))>max(abs(tt.a-x),abs(tt.b-x))){
                index=(p+j)%n;
                t=tt;
            }
        }

        c[p]=t;
        c[index]=t;
        cout<<p+1;
        cout<<" ";
        cout<<index+1<<endl;

    };
    for(int i=0;i<m;i++){
        for(int j=0;j<v[i];j++){
            f(j);
        }
    }





}