#include <bits/stdc++.h>
using namespace std;
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int N;
if (!(cin >> N)) return 0;
vector<int> a(N+1);
int maxa = 0;
long long S = 0;
for (int i = 1; i <= N; ++i){
cin >> a[i];
S += a[i];
maxa = max(maxa, a[i]);
}
int MAXS = (int)S;
int LIMIT = MAXS + maxa + 5; // giới hạn x chúng ta quan tâm
vector<char> dp_full(MAXS+1, 0);
dp_full[0] = 1;
for (int i = 1; i <= N; ++i){
// iterate backwards to avoid overwrite
for (int s = MAXS - a[i]; s >= 0; --s){
if (dp_full[s]) dp_full[s + a[i]] = 1;
}
}
if ((S % 2) != 0 || !dp_full[S/2]) {
cout << 0 << '\n';
return 0;
}
vector< vector<int> > pref_lists(N+1), suf_lists(N+2);
{
vector<char> cur(MAXS+1, 0);
cur[0] = 1;
pref_lists[0].push_back(0);
for (int i = 1; i <= N; ++i){
vector<int> new_sums;
// for each existing sum s, s+a[i] becomes reachable
for (int s : pref_lists[i-1]){
int ns = s + a[i];
if (!cur[ns]) { // not yet set
cur[ns] = 1;
new_sums.push_back(ns);
}
}
// merge lists: previous sums remain, plus new ones
pref_lists[i] = pref_lists[i-1];
if (!new_sums.empty()){
pref_lists[i].insert(pref_lists[i].end(), new_sums.begin(), new_sums.end());
}
}
}
{
vector<char> cur(MAXS+1, 0);
cur[0] = 1;
suf_lists[N+1].push_back(0);
for (int i = N; i >= 1; --i){
vector<int> new_sums;
for (int s : suf_lists[i+1]){
int ns = s + a[i];
if (!cur[ns]) {
cur[ns] = 1;
new_sums.push_back(ns);
}
}
suf_lists[i] = suf_lists[i+1];
if (!new_sums.empty()){
suf_lists[i].insert(suf_lists[i].end(), new_sums.begin(), new_sums.end());
}
}
}
for (int i = 0; i <= N+1; ++i){
sort(pref_lists[i].begin(), pref_lists[i].end());
pref_lists[i].erase(unique(pref_lists[i].begin(), pref_lists[i].end()), pref_lists[i].end());
if (i <= N+1) {
if (i <= N+1 && !suf_lists[i].empty()) {
sort(suf_lists[i].begin(), suf_lists[i].end());
suf_lists[i].erase(unique(suf_lists[i].begin(), suf_lists[i].end()), suf_lists[i].end());
}
}
}
unordered_map<int,int> cnt;
cnt.reserve(100000);
vector<char> Si(MAXS+1, 0);
for (int i = 1; i <= N; ++i){
fill(Si.begin(), Si.end(), 0);
const vector<int> &L = pref_lists[i-1];
const vector<int> &R = suf_lists[i+1];
for (int p : L){
for (int q : R){
int s = p + q;
if (!Si[s]){
Si[s] = 1;
// produce x candidates from s
long long x1 = 2LL * s - S + a[i];
if (x1 > 0 && x1 <= LIMIT) cnt[(int)x1]++;
long long x2 = S - a[i] - 2LL * s;
if (x2 > 0 && x2 <= LIMIT) cnt[(int)x2]++;
}
}
}
}
vector <int> ans;
for (auto &pr : cnt){
if (pr.second == N) ans.push_back(pr.first);
}
sort(ans.begin(), ans.end());
cout << ans.size() << '\n';
if (!ans.empty()){
for (size_t i = 0; i < ans.size(); ++i){
if (i) cout << ' ';
cout << ans[i];
}
cout << '\n';
}
return 0;
}
