#include <iostream>
#include <algorithm>
#include <cstdio>
#include <string>

#define ll long long

using namespace std;

int main(){

   int d;
   cin>>d;

   int tmp;
   int f=0,s=0,c=0;
   for(int i=0;i<=d;++i){
      if(!i) cin>>c;
      else{
          cin>>tmp;
          if(i%2) s+=tmp;
          else f+=tmp;
      }
   }
   
   int dem=2;
   if((d%2)&&f==0) dem=1;
   if(!(d%2)&&s==0) dem=1;
   if(s==0&&f==0) dem=0;
   
   cout<<dem<<endl;
   cout<<c;
   if(dem>=1) cout<<" "<<(d%2 ? s : f);
   if(dem==2) cout<<" "<<(d%2 ? f : s);
   cout<<endl;

   return 0;
}