import java.io.*;
import java.util.StringTokenizer;

class Main{

static final PrintWriter out=new PrintWriter(System.out);

public static void main(String[] args) throws IOException{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String line="";
while((line=br.readLine())!=null&&!line.isEmpty()){
int d=Integer.parseInt(line);
int[] a=new int[d+1];
StringTokenizer st=new StringTokenizer(br.readLine());
for(int i=0;i<=d;i++) a[i]=Integer.parseInt(st.nextToken());
for(int i=d;i>=3;i--) a[i-2]+=a[i];
int dd=a[2]==0?a[1]==0?0:1:2;
out.println(dd);
if(dd==0) out.println(a[0]);
if(dd==1) out.printf("%d %d\r\n",a[0],a[1]);
if(dd==2) out.printf("%d %d %d\r\n",a[0],a[1],a[2]);
out.flush();
}
}
}