HackerRank C++ Accessing Inherited Functions

You are given three classes A, B and C. All three classes implement their own version of func.

In class A, func multiplies the value passed as a parameter by 2:
In class B, func multiplies the value passed as a parameter by 3:
In class C, func multiplies the value passed as a parameter by 5:
You are given a class D
You need to modify the class D and implement the function update_val which sets D's val to new_val by manipulating the value by only calling the func defined in classes A, B and C.

#include<iostream>

using namespace std;

int callA=0;
int callB=0;
int callC=0;
class A
{
protected:
  
   void func(int  & a)
   {
      a=a*2;
      callA++;
   }
};

class B
{
protected:
   void func(int & a)
   {
      a=a*3;
      callB++;
   }
};

class C
{
protected:
   void func(int & a)
   {
      a=a*5;
      callC++;
   }
};

class D : public A,public B,public C
{
 int val;
 public:
  //Initially val is 1
   D()
   {
    val=1;
   }

   //Implement this function
   void update_val(int new_val)
   {
          int a = new_val;
     while ( a %2 == 0)
     {
         a = a/2;
         A::func(val);
     }
     while ( a % 3 == 0)
     {
         a = a/3;
         B::func(val);
     }
     while ( a % 5 == 0)
     {
         a = a/5;
         C::func(val);
     }
   
   }
   //For Checking Purpose
   void check(int); //Do not delete this line.
};

void D::check(int new_val)
{
       update_val(new_val);
       cout<<"Value = "<<val<<endl<<"A's func called "<<callA<<" times "<<endl<<"B's func called "<<callB<<" times "<<endl<<"C's func called "<<callC<<" times"<<endl;
}


int main()
{
   D d;
   int new_val;
   cin>>new_val;
   d.check(new_val);


}