// IZI IZI
// Real talk
#include <bits/stdc++.h>

using namespace std;

#define sz(a) (int)a.size()
#define all(x) (x).begin(),(x).end()
#define vi vector <int>
#define pb push_back
#define mp make_pair
#define ll long long
#define sc scanf
#define pf printf
#define f first
#define s second
#define y1 dadssda

const int inf = (int)1e9;
const int mod = inf + 7;
const double pi = acos(-1.0);
const double eps = 1e-9;

/*
int bpow(int x, int e, int p) {
    if (e == 0) return 1;
    if (e % 2) return ((bpow(x, e - 1, p)) * (x)%p) % p;
    else {
        int k = bpow(x, e / 2, p);
        return ((k%p) * (k%p)) %p;
    }
}
int gcd(int a,int b) { return b?gcd(b,a%b):a;}
*/

const int days[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
// /////////////////////////////////////////////////////////////////////


int n;
vector<pair<int, int> > ans;
set<pair<int, int> > s;

bool ok(int l1, int r1, int l2, int r2){
	if(r1 <= l2 || r2 <= l1) return false;
	return true;
}
int main(){
	//freopen("in.in", "r", stdin);
    //freopen("out.out", "w", stdout);
    cin >> n;
    for(int i = 0, l, r; i < n; ++i){
    	cin >> l >> r;
    	s.insert(mp(min(l, r), max(l, r)));
    }
    while(true){
    	set<pair<int ,int> > :: iterator it;
    	int maxi = -inf;
    	bool okei = 0;
    	for (set <pair<int, int> > :: iterator i = s.begin(); i != s.end(); ++i ){
    		int cnt = 0;
    		int l1 = (*i).f;
    		int r1 = (*i).s;
    		for (set <pair<int, int> > :: iterator j = s.begin(); j != s.end(); ++j){
    		    if(j == i) continue;
    		    int l2 = (*j).f;
    		    int r2 = (*j).s;
    		    if(ok(l1, r1, l2, r2)){
    		    	okei = 1;
    		    	cnt++;
    		    }
    		}
    		if(cnt > maxi){
    			maxi = cnt;
    			it = i;
    		}
    	}
    	if(okei == 0) break;
    	int l = (*it).f;
    	int r = (*it).s;
    	s.erase(mp(l, r));
    }
    cout << sz(s) << endl;
    for (set <pair<int, int> > :: iterator i = s.begin(); i != s.end(); ++i ){
    	cout << (*i).f << " " << (*i).s << endl;
    }
    return 0;
}