import java.util.concurrent.Semaphore;

class H2OMachine {

    String[] molecule;
    int count;

    static Semaphore h;
    static Semaphore o;
    static Semaphore hHere;
    static Semaphore oHere;
    static Semaphore lock;

    public H2OMachine() {
        molecule = new String[3];
        count = 0;
        h = new Semaphore(2);
        o=new Semaphore(1);
        hHere = new Semaphore(0);
        oHere = new Semaphore(0);
        lock = new Semaphore(0);
    }

    public void hydrogen() throws InterruptedException {
        // TODO: 3/29/20 synchronized logic here
        h.acquire();
        oHere.acquire(); //ceka info dali stignal O
        hHere.release();
        lock.acquire();
        System.out.println("The molecule is formed");
        h.release();

    }

    public void oxygen() throws InterruptedException {
        // TODO: 3/29/20 synchronized logic here
        o.acquire(); //od pollot se vadi element od kislorod
        oHere.release(2); //ke bide koordinator, znaci ke izvesti 2 h atomi deka pristignal
        hHere.acquire(2); //ceka da doznae dali i dva H atomi pristignale
        lock.release(2);
        System.out.println("The molecule is formed");
        o.release();
    }
}
class H2OThread extends Thread {

    H2OMachine molecule;
    String atom;

    public H2OThread(H2OMachine molecule, String atom){
        this.molecule = molecule;
        this.atom = atom;
    }

    public void run() {
        if ("H".equals(atom)) {
            try {
                molecule.hydrogen();
            }
            catch (Exception e) {
            }
        }
        else if ("O".equals(atom)) {
            try {
                molecule.oxygen();
            }
            catch (Exception e) {
            }
        }
    }
}

public class Main
{
    public static void main(String[] args) {

        // TODO: 3/29/20 Simulate with multiple scenarios
        H2OMachine molecule = new H2OMachine();

        Thread t1 = new H2OThread(molecule,"H");
        Thread t2 = new H2OThread(molecule,"O");
        Thread t3 = new H2OThread(molecule,"H");
        Thread t4 = new H2OThread(molecule,"O");

        t2.start();
        t1.start();
        t4.start();
        t3.start();
    }
}