#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 500*500+1;
typedef array<int,MX> B;
int N, a[500];
bitset<MX> all;
B b;
int sum = 0;
void ad(B& b, int x) {
sum += x;
FORd(i,x,MX) {
b[i] += b[i-x];
if (b[i] >= MOD) b[i] -= MOD;
}
}
void del(B& b, int x) { // b[i]+b[i-x] = b2[i], b[i] = b2[i]-b[i-x]
sum -= x;
FOR(i,x,MX) {
b[i] -= b[i-x];
if (b[i] < 0) b[i] += MOD;
}
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
all.flip();
cin >> N;
b[0] = 1;
F0R(i,N) {
cin >> a[i];
ad(b,a[i]);
}
if (sum % 2 != 0 || !b[sum/2]) {
cout << 0;
exit(0);
}
F0R(i,N) {
del(b,a[i]);
bitset<MX> cur;
for (int j = 0; 2*j < sum; ++j) if (b[j]) cur[sum-2*j] = 1;
ad(b,a[i]);
all &= cur;
}
vi v;
FOR(i,1,MX) if (all[i]) v.pb(i);
cout << sz(v) << "\n";
for (int i: v) cout << i << " ";
}
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( )
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/
