#include<iostream>
#include<vector>
#include<map>
#include<set>
#include<cassert>
#include<cassert>
#include<unordered_map>
#include<unordered_set>
#include<functional>
#include<queue>
#include<stack>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<sstream>
#include<iomanip>
#include<cstdio>
#include<cstdlib>
#include<numeric>
#include<random>
#include<chrono>
#include<bitset>
using namespace std;

#define all(x) (x).begin(), (x).end()
#define pb push_back
#define xx first
#define yy second
#define sz(x) (int)(x).size()
#define gc getchar
#define IO ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define mp make_pair

#ifndef ONLINE_JUDGE
#  define LOG(x) (cerr << #x << " = " << (x) << endl)
#else
#  define LOG(x) ((void)0)
#endif

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

const double PI=3.1415926535897932384626433832795;
const ll INF = 1LL<<62;
const ll MINF = -1LL<<62;

template<typename T> T getint() {
	T val=0;
	char c;
	
	bool neg=false;
	while((c=gc()) && !(c>='0' && c<='9')) {
		neg|=c=='-';
	}

	do {
		val=(val*10)+c-'0';
	} while((c=gc()) && (c>='0' && c<='9'));

	return val*(neg?-1:1);
}

//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); uniform_int_distribution<int>(0, n-1)(rng)

const int MAXN=5001;
int par[MAXN], banned=0;
vector<int> adj[MAXN];
vector<int> comp;
vector<int> color[2];
int st0[MAXN], st1[MAXN];

void dfs0(int x, int c=0) {
    st0[x]=1;
    comp.pb(x);
    color[c].pb(x);
    for(auto i:adj[x]) if(!st0[i]) dfs0(i,c^1);
}

int matching = 0;

bool dfs1(int x) {
    st1[x]=1;
    for(auto i:adj[x]) {
        if(!st1[i] && i!=banned) {
		    if(par[i]==0 || (par[i]!=x && !st1[par[i]] && dfs1(par[i]))) {
				if(par[i]==0) matching++;

				par[x]=i;
				par[i]=x;
                return true;
            }
        }
    }
    return false;
}

int match(bool early=false) {
    bool done_smth;
    do {
        for(int i:comp) {
            st1[i]=0;
        }
    
        done_smth=false;
        for(int i:color[0]) {
            if(i!=banned && !st1[i] && par[i]==0) {
                done_smth|=dfs1(i);
				if(done_smth && early) break ;
            }
        }
    }while(done_smth);
        
    return matching;
}

vector<int> answer(int ind) {
    if(st0[ind]) return {};
    color[0].clear();
    color[1].clear();

    comp.clear();

    dfs0(ind);
	if(sz(color[0])>sz(color[1])) color[0].swap(color[1]);

    for(int i:comp) {
        par[i]=0;
    }
    
    int max_matching=match();
    vector<int> ans;

    for(int i:comp) {
        banned=i;
        
        if(par[banned]) {
            par[par[banned]]=0;
            par[banned]=0;
			matching--;
        }

        int matching=match(true);
        if(matching==max_matching) ans.pb(i);
    }
    
    return ans;
}

int main() {
	IO;
    int n;
    cin>>n;
    vector<pair<int,int>> t(n);
    map<pair<int,int>, int> conv;
    for(int i=0;i<n;++i) {
        cin>>t[i].xx>>t[i].yy;
        conv[t[i]]=i+1;
    }
    
    for(int i=0;i<n;++i) {
        pair<int,int> pt1={t[i].xx+1, t[i].yy};
        pair<int,int> pt2={t[i].xx, t[i].yy+1};
        if(conv.count(pt1)) {
            adj[conv[pt1]].pb(i+1);
            adj[i+1].pb(conv[pt1]);
        }

        if(conv.count(pt2)) {
            adj[conv[pt2]].pb(i+1);
            adj[i+1].pb(conv[pt2]);
        }
    }
    
    vector<int> ans;
    for(int i=1;i<=n;++i) {
        for(auto j:answer(i)) ans.pb(j);
    }
    
    cout<<sz(ans)<<"\n";
    for(auto i:ans) cout<<t[i-1].xx<<" "<<t[i-1].yy<<"\n";
    
	return 0;
}