How to initialize const member , that are not static

I know how to initialize const member in the initializer list, but that requires to know the value to be assigned already when calling the constructor. From what I understand, in java it's possible to initialize a final member in the constructor body, but I haven't seen an equivalent in c++ ( Java's final vs. C++'s const )

But what to do when the initialization is relatively complex? The best I could come up, is to have an initialization function that returns directly an instance. Is there something more concise?

Here is an example (https://ideone.com/TXxIHo)

class Multiplier
{
   const int mFactor1;
   const int mFactor2;
   static void initializationLogic (int & a, int & b, const int c )
   {
       a = c * 5;
       b = a * 2;
    }

  public:
   Multiplier (const int & value1, const int & value2)
     : mFactor1(value1), mFactor2(value2)
     {};
   /*
   //this constructor doesn't initialize the const members
   Multiplier (const int & value)
     {
        initializationLogic(mFactor1,mFactor2, value);
     };
    */
   //this initializes the const members, but it's not a constructor
   static Multiplier getMultiplierInstance (const int & value)
   {
       int f1, f2;
       initializationLogic(f1,f2, value);
       Multiplier obj(f1,f2);
       return obj;
   }