/* Author : Mychecksdead */
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
const int N = 510, M = 510, MX = 520*520;
int n, a[N], S = 0;
bitset<MX/2> dp[N];
void solve(){
cin >> n;
bool ok = 1;
for(int i = 1; i <= n; ++i){
cin >> a[i];
S += a[i];
if(a[i] % 2 != a[1] % 2){
ok = 0;
}
}
if(!ok || S % 2){
cout << 0;
return;
}
vector<int> used(M);
vector<int> s;
s.pb(0);
for(int i = 1; i <= n; ++i){
if(!used[a[i]]) s.pb(i);
used[a[i]] = 1;
}
for(int i: s){
dp[i][0] = 1;
for(int l = 1; l <= n; ++l){
if(i == l) continue;
dp[i] = dp[i] | (dp[i] << a[l]);
}
}
vector<int> possible;
for(int x = 2 - (a[1] % 2); x <= S; x += 2){
ok = 1;
a[0] = x;
for(int i: s){
bool state1 = 0, state2 = 0;
int req = -1, req1 = -1;
int c = S + x - a[i];
req = c >> 1;
if(req > S/2) req = c - req;
if(req <= S/2)
state1 = dp[i][req];
if(i > 0){
req1 = (c >> 1) - x;
if(req1 >= 0){
if(req1 > S/2) req1 = c - req1;
if(req1 <= S/2)
state2 = dp[i][req1];
}
}
if(!(state1 | state2)){
ok = 0;
break;
}
}
if(ok){
possible.pb(x);
}
}
cout << possible.size() << '\n';
for(int p: possible) cout << p << ' ';
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
solve();
return 0;
}
