#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD 1000003
#define INF 100000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	int d;
	int a[10101] = {};
	cin >> d;
	REP(i, d + 1) {
		cin >> a[i];
	}
	for (int i = d; 2 < i; --i) {
		a[i - 2] += a[i];
	}
	if (a[2]) {
		cout << 2 << endl;
		cout << a[0] << " " << a[1] << " " << a[2] << endl;
	}
	else if (a[1]) {
		cout << 1 << endl;
		cout << a[0] << " " << a[1] << endl;
	}
	else {
		cout << 0 << endl;
		cout << a[0] << endl;
	}
	return 0;
}