#include <iostream>
#include <memory>

template <typename T>
struct Node
{
    T value;
    std::unique_ptr<Node<T>> next;
};

template <typename T>
std::size_t countStep(const std::unique_ptr<Node<T>>& node, std::size_t i)
{
    return (node)
         ? countStep(node->next, i + 1)
         : i;
}

template <typename T>
std::size_t count(const std::unique_ptr<Node<T>>& head)
{
    return countStep(head, 0);
}

int main()
{
    using NodeT = Node<int>;

    auto head = std::make_unique<NodeT>(NodeT{5, nullptr});
    head->next = std::make_unique<NodeT>(NodeT{12, nullptr});
    head->next->next = std::make_unique<NodeT>(NodeT{35, nullptr});
    head->next->next->next = std::make_unique<NodeT>(NodeT{1, nullptr});

    std::cout << "Size: " << count(head) << '\n';
}