mutex

#include <thread>
#include <vector>
#include <iostream>
#include <mutex>

std::mutex mutex;

void hello(int x) {
    mutex.lock();
    std::cout << "Hello, Concurrent World!" << x << '\n';
    mutex.unlock();
    return;
}

int main() {
    int x;
    std::vector<std::thread> arr;
    std::cin >> x;
    for (int i = 0; i < x; i++) {
        arr.push_back(std::thread(hello, i));
    }
    for (int i = 0; i < x; i++) {
        arr[i].join();
    }
    return 0;
 }