How to copy values from a non const vector to a const vector in C++?

I have the following class where I have a private member vectortest which I would like to use as a computation variable for operations within the class member functions. Then, I would copy the computed vector to another vector cvectorin, which is a public member but a constant so that the contents cannot be modified, yet is accessible. I tried the following (both assignment as well as std::copy):

class constVecTest
{
  private:
    vector<int> vectortest;
  public:
    constVecTest(vector<int> vin);
    const vector<int> cvectorin;
    vector<int> vectorin;
    void vecOp1();
    void vecOp2(vector<int> vin);
};

constVecTest::constVecTest(vector<int> vin)
{
  vecOp1();
  vecOp2(vin);
}

void constVecTest::vecOp1()
{
  vectortest = {1, 0, 1, 0, 1};
  // cvectorin = vectortest;
  copy(vectortest.begin(), vectortest.end(), back_inserter(cvectorin));
}

void constVecTest::vecOp2(vector<int> vin)
{
  vectortest = vin;
  vectorin = vectortest;
}


int main()
{
  vector<int> input {1, 2, 3, 4, 5}, cvo, cvc;

  constVecTest cvt(input);
  cvo = cvt.vectorin;
  cvc = cvt.cvectorin;
  
  return 0;
}

But I get the error:

error: passing ‘const std::vector<int>’ as ‘this’ argument discards qualifiers [-fpermissive]

I'm new to vectors and couldn't find any good example on such a scenario. How do I achieve what I intend to? If the above approach is not the right one, I would be glad to learn a new alternative.