public static void whatsNext(List<long> arr)
{
    var tzc = 0L;
    
    if (arr.Count % 2 == 0) {
        tzc = arr[^1];
        arr.RemoveAt(arr.Count - 1);
    }
    
    var toc = arr[^1];
    
    if (arr.Count > 1) {
        --arr[^2];
    }
    
    arr[^1] = 1;
    arr.Add(1 + tzc);
    arr.Add(toc - 1);
    
    for (var i = 1; i < arr.Count - 1; ) {
        if (arr[i] == 0) {
            arr[i - 1] += arr[i + 1];
            arr.RemoveRange(i, 2);
        } else {
            ++i;
        }
    }
    
    if (arr[^1] == 0) {
        arr.RemoveAt(arr.Count - 1);
    }
    
    Console.WriteLine(arr.Count);
    Console.WriteLine(string.Join(' ', arr));
}