#include <cstdio>
#include <array>
#include <cassert>
using namespace std;
const int maxN = 500;
const int maxA = 501;
using posstype = array<bool, maxA*maxN/2>;
constexpr int ilog2(int n){
return 31^__builtin_clz(n);
}
constexpr int ilog2c(int n){
return ilog2(n)+!!(n&(n-1));
}
array<posstype, ilog2(maxN)+2> logCache{};
array<int, ilog2(maxN)+2> logIndex{};
int N, sum;
array<int, maxN+1> a{};
template<bool different>
void calc(posstype& possout, const posstype& possin, int add){
//printf("+%d\n", add);
if constexpr(different)
for(int j=0; j <= sum/2; j++){
possout[j] = possin[j];
}
for(int j=sum/2-add; j >= 0; j--){
if(possin[j]){
possout[j+add] = true;
}
}
}
void calcrange(posstype& possout, const posstype& possin, int idfirst, int idend){
//printf("%d -> %d\n", idfirst, idend);
calc<true>(possout, possin, a[idfirst]);
for(int idp=idfirst+1; idp<idend; idp++){
calc<false>(possout, possout, a[idp]);
}
}
void recalcLog(int startLevel, int start){
//printf("%d\n", startLevel);
int curend = logIndex[startLevel-1];
assert(curend >= start);
assert(startLevel >= 1 && startLevel <= ilog2(N)+1);
for(int level = startLevel; level <= ilog2(N)+1; level++){
int shift = ilog2(N)+1-level;
int block = 1 << shift;
if(block+start > curend){
logCache[level] = logCache[level-1];
}else{
calcrange(logCache[level], logCache[level-1], curend-block, curend);
curend -= block;
}
logIndex[level] = curend;
}
assert(curend == start);
}
void addToLog(int add){
for(int i=0; i<=ilog2(N)+1; i++){
calc<false>(logCache[i], logCache[i], add);
}
}
int main(){
scanf("%d\n", &N);
array<bool, maxA> already{};
sum = 0;
for(int i=0; i<N; i++){
scanf("%d", &a[i]);
sum += a[i];
}
array<int, maxA*maxN> poss{};
logCache[0][0] = true;
logIndex[0] = N;
recalcLog(1, 0);
if(!logCache[ilog2(N)+1][sum/2]){
printf("0\n");
return 0;
}
int duplicate = 0;
for(int i=0; i<N; i++){
int part = sum-a[i];
if(already[a[i]]){
addToLog(a[i-1]);
duplicate++;
continue;
}
#ifdef DEBUG
printf(" ------- %d(%d) ------ \n", i, a[i]);
#endif
already[a[i]] = true;
int startLevel = ilog2(N)+1;
while(logIndex[startLevel] < i+1){
startLevel--;
}
startLevel++;
#ifdef DEBUG
printf("level: %d/%d\n", startLevel, ilog2(N)+1);
#endif
if(startLevel <= ilog2(N)+1)
recalcLog(startLevel, i+1);
if(i)
addToLog(a[i-1]);
posstype& possreferee = logCache[ilog2(N)+1];
for(int idw=0; idw<=part/2; idw++){
if(possreferee[idw]){
#ifdef DEBUG
printf("%d/%d => %d\n", idw, part/2, part-idw*2);
#endif
poss[part-idw*2]++;
}
}
}
int count = 0;
for(int i=0; i<sum; i++)
count += poss[i] == N-duplicate;
printf("%d\n", count);
if(count){
for(int i=0; i<sum; i++){
if(poss[i] == N-duplicate){
printf("%d ", i);
}
}
printf("\n");
}
}
