#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll goal = 5e17;

int N;
ll A[45], B[45], C[45];
int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> N;
    for(int i = 0;i < N;i++){
        cin >> A[i] >> B[i];
        A[i] -= goal, B[i] -= goal;
        C[i] = (A[i] - B[i]);
    }
    vector<int> cid;
    for(int i = 0;i < N;i++)cid.push_back(i);
    vector<pair<int, int>> ans;
    for(int t = 0;t < 50;t++){
        int s, g;
        if(t < 35){
            sort(cid.begin(), cid.end(), [](int x, int y){
                return (A[x] - B[x]) < (A[y] - B[y]);
            });
            s = cid.front();
            g = cid.back();
            if(abs(A[s] - B[s]) < abs(A[g] - B[g]))swap(s, g);
            ll mn = goal * 2;
            for(int i : cid){
                ll v = (A[s] - B[s]) + (A[i] - B[i]);
                if(mn > abs(v)){
                    mn = abs(v);
                    g = i;
                }
            }
        }else if(t < 40){
            sort(cid.begin(), cid.end(), [](int x, int y){
                return (A[x] - B[x]) < (A[y] - B[y]);
            });
            s = 0;
            ll mn = goal * 2;
            for(int i : cid){
                ll v = (A[s] - B[s]) + (A[i] - B[i]);
                if(mn > abs(v)){
                    mn = abs(v);
                    g = i;
                }
            }
        }else{
            sort(cid.begin(), cid.end(), [](auto x, auto y){
                return (A[x] + B[x]) / 2 < (A[y] + B[y]) / 2;
            });
            s = 0;
            ll mn = goal * 2;
            for(int i : cid){
                ll v = (A[0] + A[i]) / 2 + (B[0] + B[i]) / 2;
                if(mn > abs(v)){
                    mn = abs(v);
                    g = i;
                }
            }
        }
        /* for(auto [a, b] : cid){
            cerr << a << " ";
        }
        cerr << endl; */
        if(s == g)continue;
        A[s] = A[g] = (A[s] + A[g]) / 2;
        B[s] = B[g] = (B[s] + B[g]) / 2;
        ans.push_back({s, g});
    }
    cout << ans.size() << endl;
    for(auto [a, b] : ans){
        cout << a + 1 << " " << b + 1 << endl;
    }
    return 0;
}