#include <fstream>
#include <algorithm>
#define DEF 10001

using namespace std;

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

int n, v[DEF], nr_sol, sol[DEF];
bool fvr[50001];

int main () {
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> v[i];
    sort (v + 1, v + n + 1);
    for (int i = 1; i <= n; i++) {
        if (fvr[v[i]] == 0) {
            fvr[v[i]] = 1;
            sol[++nr_sol] = v[i];
        }
        for (int j = 1; j <= v[n] - v[i]; j++) {
            if (fvr[j])
                fvr[v[i] + j] = 1;
        }
    }

    fout << nr_sol << "\n";
    for (int i = 1; i <= nr_sol; i++)
        fout << sol[i] << " ";

    return 0;
}