Print sequence of number using 3 thread

I am learning multi threading concept.I am trying to print sequence of number using 3 thread(using 2 thread its working).My program hang after print 1,2,3.

Code:

#include <iostream>
#include <string>
#include <thread>
#include <mutex>
#include <condition_variable>
using namespace std;
std::mutex MUT;
std::condition_variable cv;

enum class table {EVEN,ODD,HALF};

table t=table::ODD;

void even(int &r)
{
    while(r<20)
    {
        unique_lock<mutex>l1(MUT);
        cv.wait(l1,[](){ return t==table::EVEN;});
        cout<<"Thread 2 "<<r++<<endl;
        t=table::HALF;
        l1.unlock();
        cv.notify_one();
    }
}   

void odd(int &s)
{
    while(s<20)
    {   
        unique_lock<mutex>l2(MUT);
        cv.wait(l2,[](){ return t==table::ODD;});
        cout<<"Thread 1 "<<s++<<endl;
        t=table::EVEN;
        l2.unlock();
        cv.notify_one();
    }
}

void half(int &u)
{
    while(u<20)
    {   
        unique_lock<mutex>l3(MUT);
        cv.wait(l3,[](){ return t==table::HALF;});
        cout<<"Thread 3 "<<u++<<endl;
        t=table::ODD;
        l3.unlock();
        cv.notify_one();

    }

}

int main()
{
int x=1;
thread t1(odd,ref(x));  
thread t2(even,ref(x)); 
thread t3(half,ref(x));

t1.join();
t2.join();
t3.join();

return 0;
}

Output shown:
Thread 1 1
Thread 2 2
Thread 3 3

After this no output.

Please let me know where i am doing wrong using 3 threads.
Thanks for your help