#include<bits/stdc++.h>
using namespace std;
const int maxN = 500 + 5;
const int bsSize = maxN * maxN + 10;
const int limit = 18000;
int n;
int a[maxN];
int cnt[maxN];
bitset<bsSize> dp[2][maxN];
bitset<limit> dp1[2][maxN];
int main() {
cin >> n;
int sum = 0;
int gc = 0;
for (int i = 1; i<=n; i++) {
cin >> a[i];
gc = __gcd(a[i], gc);
}
for (int i = 1; i<=n; i++) {
a[i]/=gc;
if ((a[i] & 1) == 0) {
printf("0\n");
return 0;
}
if (cnt[a[i]] == 0) cnt[a[i]] = i;
sum+=a[i];
}
for (int i = 1; i <= n + 1; i++) {
dp[0][i].set(0);
dp1[0][i].set(0);
}
for (int i = 1; i<=n; i++) {
for (int j = 1; j <= n + 1; j++) {
if (j<= n && cnt[a[j]] != j) continue;
if (sum < limit) {
if (i == j) {
dp1[i&1][j] = dp1[(i&1) ^ 1][j];
} else {
dp1[i&1][j] = dp1[(i&1) ^ 1][j] | (dp1[(i&1) ^ 1][j] << a[i]);
}
} else {
if (i == j) {
dp[i&1][j] = dp[(i&1) ^ 1][j];
} else {
dp[i&1][j] = dp[(i&1) ^ 1][j] | (dp[(i&1) ^ 1][j] << a[i]);
}
}
}
}
if (sum & 1) {
printf("0\n");
return 0;
}
if ((sum >= limit && dp[n&1][n + 1][sum/2] == 0) || (sum < limit && dp1[n&1][n + 1][sum/2] == 0)) {
printf("0\n");
return 0;
}
vector<int> ans;
for (int i = 1; i <= sum; i+=2) {
bool ok = true;
for (int j = 1; j<= n; j++) {
if (cnt[a[j]] != j) continue;
int totSum = sum - a[j] + i;
if (totSum % 2 == 1) ok = false;
if ((sum>= limit && dp[n&1][j][totSum/2] == 0) || (sum < limit && dp1[n&1][j][totSum/2] == 0)) ok = false;
}
if (ok) ans.push_back(i);
}
cout << ans.size() << endl;
for (int i:ans) {
cout << i * gc << " ";
}
cout << endl;
}
