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

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 (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

template < typename T >
void vprint(T &V){
	for(auto v : V){
    	cout << v << " ";
	}
	cout << endl;
}

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

    // input
    ll D;
    cin >> D;
    D++;

    vector<ll> B(D);

    FOR(i, 0, D){
        cin >> B.at(i);
    }
    reverse(ALL(B));

    FOR(i, 0, D-3){
        B[i+2] += B[i];
        B[i] = 0;
    }

    // vprint(B);

    if(B[D-3]!=0){
        p(2);
        cout << B[D-1] << ' ' << B[D-2] << ' ' << B[D-3] << endl;
    }
    else if(B[D-2]!=0){
        p(1);
        cout << B[D-1] << ' ' << B[D-2] << endl;
    }
    else{
        p(0);
        p(B[D-1]);
    }

    
    return 0;
}