#include <bits/stdc++.h>
#define MAXN 1000
#define MAXV 50000

using namespace std;

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

int main() {
    int n, arr[MAXN], fr[MAXV + 1]={0};
    fin >> n;
    for (int i = 0; i < n; i++)
        fin >> arr[i];
    sort(arr, arr + n);
    int maxi = arr[n - 1];

    vector<int> nrs;
    for (int i = 0; i < n; i++) {
        if (fr[i])
            continue;
        nrs.push_back(arr[i]);
        fr[arr[i]] = 1;
        for (int j = 1; j < n; j++)
            if (fr[j])
                fr[arr[i] + j] = 1;
    }

    fout << nrs.size() << '\n';
    for (auto &nr: nrs)
        fout << nr << ' ';
    return 0;
}