#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define pb push_back
#define mp make_pair
#define fi first
#define se second

int n;
vector<pair<int, int> > points;
vector<vector<int> > adj;

vector<bool> vis;

bool wins(int cur) {
    vis[cur] = true;
    bool result = true;
    for(int nei : adj[cur]) {
        if(!vis[nei]) {
            if(wins(nei)) {
                result = false;
            }
        }
    }
    vis[cur] = false;
    return result;
}

void solve() {
    cin >> n;
    if(n > 1000) {
        return;
    }
    points.assign(n, mp(0, 0));
    adj.assign(n, vector<int> (0, 0));
    for(int i = 0; i < n; i++) {
        cin >> points[i].fi >> points[i].se;
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            if(abs(points[i].fi - points[j].fi) + abs(points[i].se - points[j].se) == 1) {
                adj[i].pb(j);
            }
        }
    }
    vector<pair<int, int> > ans;
    vis.assign(n, false);
    for(int i = 0; i < n; i++) {
        if(wins(i)) {
            ans.pb(points[i]);
        }
    }
    cout << (int) ans.size() << "\n";
    for(pair<int, int> p : ans) {
        cout << p.fi << " " << p.se << "\n";
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}