#include <iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<iomanip>
#include<map>
#include<queue>
#include<set>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define req(i,n) for(int i = 1;i <=  n; i++)
#define rrep(i,n) for(ll i = n-1;i >= 0;i--)
#define ALL(obj) begin(obj), end(obj)
#define RALL(a) rbegin(a),rend(a)
typedef long long ll;
typedef long double ld;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const ll INF = 1e18;
ll mod = 1e9 + 7;
int main() {
    int n; cin >> n; 
    vector<int> a(n+1); ll sum = 0,cnt=0;
    rep(i, n+1) {
        cin >> a[i]; sum += a[i];
        if (i % 2) cnt -= a[i];
        else cnt += a[i];
    }ll A = (sum + cnt) / 2 - a[0];
    ll B = (sum - cnt) / 2, C = a[0];
    if (A == 0) {
        if (B == 0) {
            cout << 0 << endl << C << endl;
        }
        else {
            cout << 1 << endl;
            cout << C << " " << B << endl;
        }
    }
    else {
        cout << 2 << endl;
        cout << C << " " << B << " " << A << endl;
    }
}