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#include <iostream>
#include <string>

class Logger {
public:
    // C++11 thread-safe local-static Singleton
    static Logger& getInstance() {
        static Logger instance;   // constructed once, destroyed at program exit
        return instance;
    }

void log(const std::string& msg) {
        ++messageCount_;
        std::cout << "[LOG #" << messageCount_ << "] " << msg << "
";
    }

int messageCount() const { return messageCount_; }

// Delete copy/move to enforce singleton semantics
    Logger(const Logger&)            = delete;
    Logger& operator=(const Logger&) = delete;

private:
    Logger() : messageCount_(0) {
        std::cout << "Logger initialised
";
    }

int messageCount_;
};

class Config {
public:
    static constexpr int    MAX_RETRIES = 3;
    static constexpr double TIMEOUT_SEC = 30.0;

static int instanceCount() { return count_; }

Config()  { ++count_; }
    ~Config() { --count_; }

private:
    static int count_;   // definition in .cpp: int Config::count_ = 0;
};

int Config::count_ = 0;

int main() {
    Logger::getInstance().log("Application started");
    Logger::getInstance().log("Config loaded");

{
        Config c1, c2;
        std::cout << "Config instances: " << Config::instanceCount() << "
";
    }
    std::cout << "Config instances: " << Config::instanceCount() << "
";
    std::cout << "MAX_RETRIES = " << Config::MAX_RETRIES << "
";

return 0;
}