import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int d = sc.nextInt();
    int r0 = 0;
    int r1 = 0;
    int r2 = 0;
    for(int i = 0; i <= d; i++) {
      int a = sc.nextInt();
      if(i == 0) r0 = a;
      r1 += a;
      if(i % 2 == 0) {
        r2 += a;
      } else {
        r2 -= a;
      }
    }
    int c = r0;
    int a = (r1 + r2 - 2 * c) / 2;
    int b = r1 - a - c;
    if(a != 0) {
      System.out.println(2);
      System.out.println(c + " " + b + " " + a);
    } else if(b != 0) {
      System.out.println(1);
      System.out.println(c + " " + b);
    } else {
      System.out.println(0);
      System.out.println(c);
    }
  }
}