#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define PB push_back
#define all(x) x.begin(),x.end()
using namespace std;
const int N = 510;
const int N2 = N * N;
const int PW = 10;
const int VL = (1 << PW);
const int oo = 2e9;
const int K = 11;
const int md = int(1e9) + 7;
vector<int> ans, nw;
int f[N2], a[N], n, pref;
int sum(int x, int y){ return (x + y) % md; }
void BAD(){
cout << 0;
exit(0);
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
f[0] = 1;
for (int i = 0; i < n; i++) {
cin >> a[i];
pref += a[i];
for (int j = pref; j >= a[i]; j--)
f[j] = sum(f[j], f[j - a[i]]);
}
if (pref & 1) BAD();
if (f[pref >> 1] == 0) BAD();
ans.clear();
for (int i = 1; i < N2; i++)
ans.PB(i);
for (int i = 0; i < n; i++){
for (int j = a[i]; j <= pref; j++)
f[j] = sum(f[j], md - f[j - a[i]]);
nw.clear();
for (int x : ans){
int sm = pref - a[i] + x;
if (sm & 1) continue;
if (f[sm >> 1] == 0) continue;
nw.PB(x);
}
ans = nw;
for (int j = pref; j >= a[i]; j--)
f[j] = sum(f[j], f[j - a[i]]);
}
cout << sz(ans) << '\n';
for (int x : ans)
cout << x << " ";
return 0;
}
