#include <bits/stdc++.h>
#define int long long
#define pll pair<int,int>
#define endl '\n'
using namespace std;
const int MOD2=998244353;
const int MOD1=1e9+7;
const int N=3e5+7;
const int LOG=20;
const long long inf=8e18+7;
int l[N],r[N],aa=0,bb=0;
vector<int>v;
int dfs(int k,int a,int b, int n){
if(k >= n){
return 0;
}
aa=a,bb=b;
if(a==l[k-1]){
return dfs(k+1,a,b+r[k-1], n)+1;
}
if(a==r[k-1]){
return dfs(k+1,a,b+l[k-1], n)+1;
}
if(b==l[k-1]){
return dfs(k+1,a+r[k-1],b, n)+1;
}
if(b==r[k-1]){
return dfs(k+1,a+l[k-1],b, n)+1;
}
return 0;
}
signed main()
{
ios_base::sync_with_stdio(0),
cin.tie(0);
int n;
cin>> n;
for(int i=0;i<n;i++){
cin>> l[i]>>r[i];
}
dfs(1,l[1],r[1],n);
if(aa==l[n-1]){
v.push_back(min(aa,bb+r[n-1]));
}
if(aa==r[n-1]){
v.push_back(min(aa,bb+l[n-1]));
}
if(bb==l[n-1]){
v.push_back(min(aa+r[n-1],bb));
}
if(bb==r[n-1]){
v.push_back(min(aa+l[n-1],bb));
}
cout<< v.size()<<endl;
sort(v.begin() , v.end());
for(int i: v){
cout<< i<<endl;
}
}
