men.enter() {

lock();
men.waiting++;
if (women.waiting || women.inside) {
    unlock();
    men.sleeping.P();
    lock();
}
men.waiting--;
men.inside++;
unlock();

}

men.leave() {

lock();
men.inside--;
if (men.inside == 0) {
    for (i = 0; i < women.waiting; i++)
       women.sleeping.V();
}
unlock();

}