#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

int D;
int a[100001];

int main(int argc, char **argv) {
	cin >> D;
	REP(i, D + 1) cin >> a[i];
	for (int i = D; i >= 3; --i) a[i - 2] += a[i];
	if (a[2] != 0) cout << 2 << endl << a[0] << " " << a[1] << " " << a[2] << endl;
	else if (a[1] != 0) cout << 1 << endl << a[0] << " " << a[1] << endl;
	else cout << 0 << endl << a[0] << endl;
	return 0;
}