#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> > coords;
vector<vector<int> > g;
vector<bool> A;
vector<bool> B;
vector<bool> vis;
vector<int> pr;
vector<bool> win;

void get_parties(int cur, bool which) {
    if(which) {
        A[cur] = true;
    } else {
        B[cur] = true;
    }
    vis[cur] = true;
    for(int nei : g[cur]) {
        if(!vis[nei]) {
            get_parties(nei, !which);
        }
    }
}

bool dfs(int a) {
    if(vis[a]) {
        return false;
    }
    vis[a] = true;
    for(int b : g[a]) {
        if(pr[b] == -1 || dfs(pr[b])) {
            pr[b] = a;
            pr[a] = b;
            return true;
        }
    }
    return false;
}

void win_a(int cur) {
    if(vis[cur]) {
        return;
    }
    vis[cur] = true;
    if(A[cur]) {
        win[cur] = true;
    }
    for(int nei : g[cur]) {
        if((A[cur] && pr[cur] != nei) || (B[cur] && pr[cur] == nei)) {
            win_a(nei);
        }
    }
}

void win_b(int cur) {
    if(vis[cur]) {
        return;
    }
    vis[cur] = true;
    if(B[cur]) {
        win[cur] = true;
    }
    for(int nei : g[cur]) {
        if((B[cur] && pr[cur] != nei) || (A[cur] && pr[cur] == nei)) {
            win_b(nei);
        }
    }
}

void solve() {
    cin >> n;
    coords.assign(1 + n, mp(0, 0));
    for(int i = 1; i <= n; i++) {
        cin >> coords[i].fi >> coords[i].se;
    }
    g.resize(1 + n);
    for(int i = 1; i <= n; i++) {
        for(int j = i + 1; j <= n; j++) {
            if(abs(coords[i].fi - coords[j].fi) + abs(coords[i].se - coords[j].se) == 1) {
                g[i].pb(j);
                g[j].pb(i);
            }
        }
    }
    A.assign(1 + n, false);
    B.assign(1 + n, false);
    vis.assign(1 + n, false);
    for(int i = 1; i <= n; i++) {
        if(!vis[i]) {
            get_parties(i, 0);
        }
    }
    pr.assign(1 + n, -1);
    for(int i = 1; i <= n; i++) {
        if(A[i]) {
            vis.assign(1 + n, false);
            dfs(i);
        }
    }
    win.assign(1 + n, false);
    vis.assign(1 + n, false);
    for(int i = 1; i <= n; i++) {
        if(A[i] && pr[i] == -1) {
            win_a(i);
        }
    }
    vis.assign(1 + n, false);
    for(int i = 1; i <= n; i++) {
        if(B[i] && pr[i] == -1) {
            win_b(i);
        }
    }
    vector<int> ans;
    for(int i = 1; i <= n; i++) {
        if(win[i]) {
            ans.pb(i);
        }
    }
    cout << (int) ans.size() << "\n";
    for(int cur : ans) {
        cout << coords[cur].fi << " " << coords[cur].se << "\n";
    }
}

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