import java.util.Scanner;


public class Main_yukicoder40 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int d = sc.nextInt();
        int[] a = new int[d + 1];
        for (int i = 0; i <= d; i++) {
        	a[i] = sc.nextInt();
        }
        
        for (int i = d; i >= 3; i--) {
        	a[i - 2] -= -a[i];
        	a[i] = 0;
        }

        if (d > 1 && a[2] != 0) {
        	System.out.println("2");
        	System.out.printf("%d %d %d\n", a[0], a[1], a[2]);
        } else if (d > 0 && a[1] != 0) {
        	System.out.println("1");
        	System.out.printf("%d %d\n", a[0], a[1]);
        } else {
        	System.out.println("0");
        	System.out.printf("%d\n", a[0]);
        }

        sc.close();
    }
}