#include<iostream>
#include<vector>
#include<map>
#include<algorithm>
#define int long long
struct dr{
int w, h;
};
std::vector<dr>v;
std::vector<dr>input;
std::vector<int>sol;
std::map<std::pair<int, int>, bool>f;
int n;
void back(dr current)
{
if(v.empty())
{
int max=std::max(current.h, current.w);
int min=std::min(current.h, current.w);
if(!f[{min, max}])
{
f[{min, max}]=true;
sol.push_back(min);
}
return;
}
for(int i=0; i<v.size(); ++i)
{
dr elim=v[i];
if(v[i].w==current.h)
{
current.w+=v[i].h;
v.erase(v.begin()+i);
back(current);
v.insert(v.begin()+i, elim);
current.w-=v[i].h;
}
if(v[i].w==current.w)
{
current.h+=v[i].h;
v.erase(v.begin()+i);
back(current);
v.insert(v.begin()+i, elim);
current.h-=v[i].h;
}
if(v[i].h==current.h)
{
current.w+=v[i].w;
v.erase(v.begin()+i);
back(current);
v.insert(v.begin()+i, elim);
current.w-=v[i].w;
}
if(v[i].h==current.w)
{
current.h+=v[i].w;
v.erase(v.begin()+i);
back(current);
v.insert(v.begin()+i, elim);
current.h-=v[i].w;
}
}
}
signed main()
{
std::cin>>n;
for(int i=0; i<n; ++i)
{
int w, h;
std::cin>>w>>h;
input.push_back({w, h});
v.push_back({w, h});
}
for(int i=0; i<v.size(); ++i)
{
dr current=v[i];
v.erase(v.begin()+i);
back(current);
v.insert(v.begin()+i, current);
}
std::sort(sol.begin(), sol.end());
std::cout<<sol.size()<<'\n';
for(int i : sol)
std::cout<<i<<'\n';
return 0;
}
