#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <iomanip>
#include <stack>
#include <queue>
#include <deque>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define pb push_back
#define ppb pop_back
#define mkp make_pair
#define F first
#define S second
#define show(a) cerr << #a <<" -> "<< a <<"\n"
#define fo(a, b, c, d) for(int (a) = (b); (a) <= (c); (a) += (d))
#define foo(a, b, c ,d) for(int (a) = (b); (a) >= (c); (a) -= (d))
//#define int ll
const int N = 505;
const int Tima = (500 * 500) + 5;
int n, sum, dp[Tima], a[N];
bool can[Tima];
vector <int> ans;
void add(int x) {
sum += x;
for(int i = sum; i >= x; --i) {
dp[i] += dp[i - x];
}
}
void del(int x) {
for(int i = x; i <= sum; ++i) {
dp[i] -= dp[i - x];
}
sum -= x;
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
dp[0] = 1;
cin >> n;
for(int i = 1; i <= n; ++i) {
cin >> a[i];
add(a[i]);
}
if((sum % 2 == 1) || (dp[sum / 2] == 0)) {
puts("0");
return 0;
}
for(int i = 0; i < Tima; ++i)
can[i] = true;
for(int i = 1; i <= n; ++i) {
del(a[i]);
for(int x = 0; x < Tima; ++x) {
if(((sum + x) % 2 == 1) || (dp[(sum + x) / 2] == 0)) {
can[x] = 0;
}
}
add(a[i]);
}
for(int i = 0; i < Tima; ++i) {
if(can[i])
ans.pb(i);
}
cout << sz(ans) <<'\n';
for(int it : ans)
cout << it <<' ';
return 0;
}
/*
If you only do what you can do,
You will never be more than you are now!
We must all suffer from one of two pains: the pain of discipline or the pain of regret.
The difference is discipline weighs grams while regret weighs tons.
*/
