#include <iostream>
#include <string>
#include <thread>
#include <mutex>

using namespace std;

const int COUNT = 20;

mutex print_mutex;

void print(string text)
{
    for (int i = 0; i < COUNT; i++)
    {
        // Acquire the mutex lock to protect the printing.
        unique_lock<mutex> lock(print_mutex);

        // Print a line.
        for (const char &ch : text) cout << ch;
        cout << '\n';

        // Release the print mutex lock.
        lock.unlock();

        // Yield to other threads.
        this_thread::yield();
    }
}

int main(void)
{
    thread hello_thread(print, "Hello, world!");
    thread go_thread(print, "Go Spartans!");

    hello_thread.join();
    go_thread.join();

    cout << endl << "Program done." << endl;
    return 0;
}