// problema economie
// solutie de 100p

#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <deque>

using namespace std;

#define NMax 1000
#define VMax 50000

ifstream fin("economie.in");
ofstream fout("economie.out");

int n, v[VMax + 3], is[VMax + 3];
vector<int> valori;

void input() {
    fin >> n;
    int x;
    for (int i = 1; i <= n; ++i) {
        fin >> x;
        v[x] = 1;
    }
}

void init() {
    is[0] = 1;
}

void update(int v) {
    for (int i = 0; i <= VMax - v; ++i) if (is[i]) is[i + v] = 1;
}

void check(int i) {
    if (!is[i] && v[i]) {
        valori.push_back(i);
        update(i);
    }
}

void solve() {
    for (int i = 1; i <= n; ++i) check(i);
    fout << valori.size() << '\n';
    for (auto m : valori) fout << m << '\n';
}

int main() {
    input();
    init();
    solve();
}