#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <stack>
#include <deque>
#include <fstream>
#include <iterator>
#include <set>
#include <map>
#include <unordered_map>
#include <iomanip>
#include <cctype>
#include <string>
#include <cassert>
#include <set>
#include <bitset>
#include <unordered_set>
#include <numeric>
#define all(a) a.begin(), a.end()
#define fast ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define pb push_back
#define ppi pair<int,pair<int,int>>
#define int int64_t
using namespace std;
// /\_/\
// (= ._.)
// / > \>
// encouraging cat
const int INF = 10000000000000000;
//const int mod = 1000000007;
const int mod = 998244353;
const int MAXN = 200005;
//ifstream fin('xor.in');
//ofstream fout('xor.out');
bool operator< (vector<int> x, vector<int> y)
{
return x[0] * x[1] < y[0] * y[1];
}
int n;
vector<vector<int>> a;
bool check(int h, int w)
{
bool ok = true;
for (int i = 0;i < n;i++)
{
if (a[i][0] == h)
{
//h -= a[i][0];
w -= a[i][1];
}
else if (a[i][0] == w)
{
//w -= a[i][0];
h -= a[i][1];
}
else if (a[i][1] == h)
{
//h -= a[i][1];
w -= a[i][0];
}
else if (a[i][1] == w)
{
//w -= a[i][1];
h -= a[i][0];
}
else
{
ok = false;
break;
}
}
return ok;
}
signed main()
{
cin >> n;
a.resize(n, vector<int> (2, 0));
int s = 0;
for (int i = 0;i < n;i++)
{
cin >> a[i][0] >> a[i][1];
s += a[i][0] * a[i][1];
}
sort(all(a));
reverse(all(a));
int h = a[0][0], w = s/h;
vector<int> res;
if (s % h == 0 && check(h, w))
{
res.pb(min(h, w));
}
h = a[0][1], w = s/h;
if (s % h == 0 && check(h, w))
{
res.pb(min(h, w));
}
if (res.size() == 2 && res[0] == res[1])
{
res.pop_back();
}
cout << res.size() << '\n';
sort(all(res));
for (auto i: res)
{
cout << i << '\n';
}
cout << '\n';
return 0;
}
