#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll d;
	cin >> d;

	vector<ll> a(d+1);
	rep(i, d+1) cin >> a[i];

	for(int i = d - 2; i >= 1; i--){
		a[i] += a[i+2];
	}

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