#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    int d;
    cin >> d;
    int a[d+1];
    for (int i=0;i<=d;i++) cin>>a[i];
    for (int i=d;i>=3;i--) a[i-2] += a[i];
    if (d >= 2 && a[2]) cout << 2 << endl << a[0] << ' ' << a[1] << ' ' << a[2] << endl;
    else if (d >= 1 && a[1]) cout << 1 << endl << a[0] << ' ' << a[1] << endl;
    else cout << 0 << endl << a[0] << endl;
    return 0;
}