#include <iostream>
#include <string>

class String_counter
{
public:
    String_counter()
    {
        value_ = prefix_ + std::to_string(++counter_);
    }
    ~String_counter()
    {
        value_ = prefix_ + std::to_string(--counter_);
    }
    static const std::string& value() { return value_; }
private:
    static int counter_;
    static const std::string prefix_;
    static std::string value_;
};

int String_counter::counter_ = 0;
const std::string String_counter::prefix_ = "s";
std::string String_counter::value_ = prefix_ + std::to_string(counter_);

int main()
{
    std::cout << String_counter::value() << std::endl;
    {
        String_counter c1;
        std::cout << String_counter::value() << std::endl;
        {
            String_counter c2;
            std::cout << String_counter::value() << std::endl;
        }
        std::cout << String_counter::value() << std::endl;
    }
    std::cout << String_counter::value() << std::endl;
    return 0;
}