D (Region 2012)

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>

#define N 205
#define M int(1e6)

using namespace std;

int a[N], n, top = 1;
bool was[M], dp[M];
vector<int> ans;

bool dfs(int mask) {
    if (was[mask])
        return dp[mask];

    was[mask] = true;

    for (int i = 0, j = 1; i < n; i++, j *= 2) {
        if ((mask & j) == 0) {
            int delta = 0;
            for (int k = 0, bit = 1; k < n; k++, bit *= 2) {
                if (mask & bit) {
                    if (!delta)
                        delta = abs(a[k] - a[i]);
                    else
                        delta = __gcd(delta, abs(a[k] - a[i]));
                }
            }
            if (delta == 1) continue;

            if (!dfs(mask | j)) {
                dp[mask] = true;
                return true;
            }
        }
    }
    dp[mask] = false;
    return false;
}

int main() {
    freopen("game.in", "r", stdin);
    freopen("game.out", "w", stdout);

    cin >> n;

    for (int i = 0; i < n; i++)
        cin >> a[i], top *= 2;

    if (n == 1) {
        cout << 1 << endl << a[0] << endl;
        return 0;
    }

    if (n > 15) {
        int gcd = a[0];
        for (int i = 1; i < n; i++)
            gcd = __gcd(a[i], gcd);

        if (gcd > 1) {
            if (n % 2 == 0) {
                cout << 0 << endl;
                return 0;
            }

            cout << n << endl;
            for (int j = 0; j < n; j++)
                cout << a[j] << " ";
                    cout << endl;
            return 0;
        }

        cout << 0 << endl;
        return 0;
    }

    was[top - 1] = true;
    dp[top - 1] = false;

    for (int i = 1, j = 0; i < top; i *= 2, j++) {
        if (!dfs(i)) {
            ans.push_back(j);
        }
    }

    cout << ans.size() << endl;
    for (int i = 0; i < ans.size(); i++)
        cout << a[ ans[i] ] << " ";
    cout << endl;


    return 0;
}