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

signed main(){
  int n;cin>>n;
  vector<int> v(n+1);
  for(int i=0;i<=n;i++)cin>>v[i];
  reverse(v.begin(),v.end());
  for(int i=0;i<n-2;i++)v[i+2]+=v[i];
  reverse(v.begin(),v.end());
  if(v[2]){
    cout<<2<<endl;
    cout<<v[0]<<" "<<v[1]<<" "<<v[2]<<endl;
  }
  else if(v[1]){
    cout<<1<<endl;
    cout<<v[0]<<" "<<v[1]<<endl;
  }
  else cout<<0<<endl<<v[0]<<endl;
}