package main

import (
	"fmt"
)

func main() {
	var d int
	fmt.Scan(&d)
	var a [10010]int
	for i := 0; i <= d; i++ {
		fmt.Scan(&a[i])
	}
	for i := d; i >= 3; i-- {
		a[i-2] += a[i]
		a[i] = 0
	}
	switch {
	case a[2] != 0:
		fmt.Println(2)
		fmt.Println(a[0], a[1], a[2])
	case a[1] != 0:
		fmt.Println(1)
		fmt.Println(a[0], a[1])
	default:
		fmt.Println(0)
		fmt.Println(a[0])
	}
}