#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=b-1;i>=a;i--)
#define all(x) (x).begin(),(x).end()
#define pb(x) push_back(x);
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
typedef long long ll;
typedef long double lld;
using namespace std;
using namespace atcoder;
const ll INF = (1ll<<60);
const double TIME_LIMIT = 0.92;
const ll BASE = 500000000000000000;

clock_t start=clock();
clock_t process=clock();
// random_device seed_gen;
// mt19937 engine(seed_gen());
mt19937 engine(0);

ll BigRandom(){
    ll res=0;
    rep(dgt,0,60){
        res*=2;
        res+=random()%2;
    }
    return res;
}

typedef pair<ll,ll> P;

const int N = 45;
const int M = 50;
ll A[N],B[N];

void Input(){
    int _n;cin >> _n;
    rep(i,0,N)cin >> A[i] >> B[i];
}

struct Solution{
    int X=0;
    vector<int> u,v;
    
    P Simulate(){
        ll a[N],b[N];rep(i,0,N)a[i]=A[i],b[i]=B[i];
        rep(i,0,X){
            ll tmp1=(a[u[i]]+a[v[i]])/2;
            ll tmp2=(b[u[i]]+b[v[i]])/2;
            a[u[i]]=tmp1;a[v[i]]=tmp1;
            b[u[i]]=tmp2;b[v[i]]=tmp2;
        }
        return P(a[0],b[0]);
    }

    lld CalcScore(){
        P res=Simulate();
        ll max_v=max(abs(BASE-res.first),abs(BASE-res.second));
        return log10(max_v);
    }

    void Output(){
        cout << X << endl;
        rep(i,0,X)cout << u[i]+1 << " " << v[i]+1 << endl;
    }
};

Solution InitSolve(){
    Solution res_sol;
    set<int> st;
    st.insert(0);
    rep(i,0,M){
        int x=random()%N;
        int y=random()%N;
        while(true){
            if(x!=y&&(st.count(x)||st.count(y))){
                break;
            }
            x=random()%N;
            y=random()%N;
        }
        res_sol.u.pb(x);
        res_sol.v.pb(y);
        res_sol.X++;
        st.insert(x);
        st.insert(y);
    }
    reverse(all(res_sol.u));
    reverse(all(res_sol.v));
    return res_sol;
}

Solution Suggest(Solution &sol){
    Solution next_sol=sol;
    lld next_score=INF;
    int idx=random()%M;
    int pre_x=sol.u[idx];
    int pre_y=sol.v[idx];
    rep(x,0,N)rep(y,0,N){
        if(x==y)continue;
        sol.u[idx]=x;
        sol.v[idx]=y;
        lld score=sol.CalcScore();
        if(chmin(next_score,score)){
            next_sol.u[idx]=x;
            next_sol.v[idx]=y;
        }
    }
    sol.u[idx]=pre_x;
    sol.v[idx]=pre_y;
    return next_sol;
}

Solution PartSuggest(Solution &sol){
    Solution next_sol=sol;
    set<int> idxs;
    int swap_size=random()%5+1;
    while(idxs.size()<swap_size){
        idxs.insert(random()%M);
    }
    vector<int> idxs_v;for(auto idx:idxs)idxs_v.pb(idx);
    sort(all(idxs_v));reverse(all(idxs_v));
    for(auto idx:idxs_v){
        int x=random()%N;
        int y=random()%N;
        while(true){
            bool break_flag=true;
            if(x==y){
                break_flag=false;
            }

            if(idx==M-1){
                if(x!=0&&y!=0){
                    break_flag=false;
                }
            }

            if(break_flag){
                break;
            }
            x=random()%N;
            y=random()%N;
        }
        next_sol.u[idx]=x;
        next_sol.v[idx]=y;
    }
    return next_sol;
}

Solution HillClimbing(Solution sol){
    int cnt=0;
    Solution now_sol=sol;
    lld now_score=now_sol.CalcScore();
    while((double)(clock()-start)/CLOCKS_PER_SEC<TIME_LIMIT){
        // Solution next_sol=Suggest(now_sol);
        Solution next_sol=PartSuggest(now_sol);
        lld next_score=next_sol.CalcScore();
        if(chmin(now_score,next_score)){
            now_sol=next_sol;
            cerr << now_score << endl;
        }
        cnt++;
    }
    cerr << "cnt: " << cnt << endl;
    return now_sol;
}

Solution SimulatedAnnealing(Solution sol){
    int cnt=0;
    Solution now_sol=sol;
    P now_score=now_sol.Simulate();
    ll now_v1=abs(BASE-now_score.first);
    ll now_v2=abs(BASE-now_score.second);
    double start_temp = 20;
    double end_temp = 2;
    double temp = start_temp;
    while((double)(clock()-start)/CLOCKS_PER_SEC<TIME_LIMIT){
        Solution next_sol=PartSuggest(now_sol);
        temp=start_temp+(end_temp-start_temp)*(clock()-start)/CLOCKS_PER_SEC/TIME_LIMIT;
        // if(max(now_v1,now_v2)>max(next_v1,next_v2)){
        //     now_v1=next_v1;
        //     now_v2=next_v2;
        //     now_sol.u[idx]=next_x;
        //     now_sol.v[idx]=next_y;
        // }
        // else{
        //     lld log_now_score = log10(max(now_v1,now_v2));
        //     lld log_next_score = log10(max(next_v1,next_v2));
        //     double prob = exp((log_next_score-log_now_score)/temp);
        //     if(prob>lld(BigRandom()%INF)/INF){
        //         now_v1=next_v1;
        //         now_v2=next_v2;
        //         now_sol.u[idx]=next_x;
        //         now_sol.v[idx]=next_y;
        //     }
        // }
        // cnt++;
        if(cnt%100==0)cerr << cnt << " " << temp << endl;
    }
    cerr << "cnt: " << cnt << endl;
    return now_sol;
}

int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    Input();
    Solution sol=InitSolve();
    // P res=sol.Simulate();
    Solution next_sol=HillClimbing(sol);
    // Solution next_sol=SimulatedAnnealing(sol);
    P next_score=next_sol.Simulate();
    ll next_v1=abs(BASE-next_score.first);
    ll next_v2=abs(BASE-next_score.second);
    cerr << next_v1 << " " << next_v2 << endl;
    next_sol.Output();
    // sol.Output();
    return 0;
}