#include <iostream>
#include <fstream>
#include <algorithm>
#include <queue>

using namespace std;

int n, v[50005], a[1005];
queue<int> sol;

int main()
{
    ifstream cin("economie.in");
    ofstream cout("economie.out");

    cin >> n;
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    
    sort(a + 1, a + n + 1);

    for (int i = 1; i <= n; ++i)
    {
        if (!v[a[i]])
        {
            v[a[i]] = 1;
            sol.push(a[i]);
            for (int j = a[i]; j <= 50000; ++j)
                if (v[j - a[i]])
                    v[j] = 1;
        }    
    }
    cout << sol.size() << '\n';
    while(!sol.empty())
    {
        cout << sol.front() << ' ';
        sol.pop();
    }


    return 0;
}