let n = Int(readLine()!)!
var a = readLine()!.split(separator: " ").map{Int($0)!}+[0,0]
for i in (3...n).sorted(by: >){
    a[i-2]+=a[i]
}
if a[2] != 0{
    print(2)
    print(a[..<3].map{String($0)}.joined(separator: " "))
}else if a[1] != 0{
    print(1)
    print(a[..<2].map{String($0)}.joined(separator: " "))
}else{
    print(0)
    print(a[0])
}