import gov.nasa.jpf.jvm.Verify;

import java.util.concurrent.Semaphore;


public class testConcurrent extends Thread{
	
	public static Semaphore sem;
	public static int in;
	
	static{
		sem = new Semaphore(1);
		in = 0;
	}
	
	public static void main(String[] args) {
		testConcurrent t1 = new testConcurrent();
		testConcurrent t2 = new testConcurrent();
		t1.start();
		t2.start();
	}

	@Override
	public void run() {
		try {
			sem.acquire();
			in++;
			Verify.assertTrue(in == 1);
			in--;
			sem.release();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	


}