How do I get virtual inheritance right?

In the example below I have my parent class and two child classes. Objects of either child are stored in a vector of parent. Looping over the vector I only see method invocations from the parent class. Please help me get the method definition and vtables right and how to avoid the slicing effect. Help, I have been doing python for too long where something like this would work.

#include <iostream>
#include <vector>


using namespace std;

int main()
{

    class A{
        public:

        virtual string print(){return string("A");};
    };

   class B: public A{
       virtual string print() final {return string("B");};
   };

   class C: public A{
       virtual string print() final {return string("C");};
   };

   vector<A> v;
   v.push_back(B());
   v.push_back(C());

   for(auto x : v){
       cout << x.print() << endl;
   }

}

=>

$g++ -std=c++11 -o main *.cpp
$main
A
A