import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
        int d = koko.nextInt();
        int[] a = new int[d+1];
        int gu = 0;
        int ki = 0;
        if(d<3){
            System.out.println(d);
            for(int i=0; i<d;i++){
                a[i] = koko.nextInt();
                System.out.print(a[i]);
                System.out.print(" ");
            }
            a[0]=koko.nextInt();
            System.out.println(a[0]);
        }else{
            a[0]=koko.nextInt();
            for(int i=1; i<d+1; i++){
                a[i] = koko.nextInt();
                if(i%2==0){
                    gu=gu+a[i];
                }else if(i%2!=0){
                    ki=ki+a[i];
                }
            }
            if(gu!=0){
                System.out.println(2);
                System.out.println(a[0]+" "+ki+" "+gu);
            }else if(gu==0&&ki!=0){
                System.out.println(1);
                System.out.println(a[0]+" "+ki);
            }else if(gu==0&&ki==0){
                System.out.println(0);
                System.out.println(a[0]);
            }
        }
    }
}