#include <thread>
#include <semaphore>
constexpr int loop = 100000;
std::binary_semaphore a{0},  b{1};

void producer() {
  for(int i = 0; i < loop; ++i) {
    a.acquire();
    b.release();
  }
}

void consumer() {
  for(int i = 0; i < loop; ++i) {
    b.acquire();
    a.release();
  }
}

int main() {
  std::thread t1(producer);
  std::thread t2(consumer);
  t1.join();
  t2.join();
  puts("done");
}