What is the Errors ?

Question

#include <iostream>
using namespace std;

class Base
{ int m;
public:
Base(int mValue){ m = mValue; cout<<"Constructing base"; }
};
class Derived: public Base
{double n;
public:

Derived(double nValue) { n =nValue; cout<<"Constructing derived"; }
};

int main(){
Base b1;

Base b2(3.0);

Derived d1
Derived d2(4.0);

return 0;
}