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

int main() {
    int D, a[10010];
    cin >> D;
    for (int i = 0; i <= D; i++) {
        cin >> a[i];
    }

    for (int i = D; i >= 3; i--) {
        a[i - 2] += a[i];
    }

    if (a[2]) {
        cout << 2 << endl
             << a[0] << " " << a[1] << " " << a[2] << endl;
    } else if (a[1]) {
        cout << 1 << endl
             << a[0] << " " << a[1] << endl;
    } else {
        cout << 0 << endl
             << a[0] << endl;
    }
}