#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-9;
const ll mod=1e9+7;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

ll n;
vi a,b;

int main(){
	cin>>n;
	a=vi(n+1);
	for(int i=0;i<=n;i++) cin>>a[i];
	for(int i=n;i>=3;i--) a[i-2]+=a[i],a[i]=0;
	for(int i=n;i>=0;i--) if(a[i]!=0||!b.empty()) b.push_back(a[i]);
	reverse(b.begin(),b.end());
	if(b.empty()) cout<<0<<endl<<0<<endl;
	else{
		int N=b.size();
		cout<<N-1<<endl;
		for(int i=0;i<N;i++) cout<<b[i]<<" \n"[i==n];
	}
}