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

int main() {
	int d;
	cin >> d;
	vector<int> b(d+1);
	for (int i = 0;i <= d;i++) {
		cin >> b[i];
	}
	for (int i = d;i >= 3;i--) {
		b[i - 2] += b[i];
	}

	int d2=0;
	if (b[2] != 0) {
		d2 = 2;
	}
	else if (b[1] != 0) {
		d2 = 1;
	}
	cout << d2 << endl;

	cout << b[0];
	if (b[2] != 0) {
		cout << ' ' << b[1] << ' ' << b[2];
	}
	else if (b[1] != 0) {
		cout << ' ' << b[1];
	}
	cout << endl;

	return 0;
}