Multi-level inheritance in OOPs

#include <iostream>

using namespace std;

 // multi-level inheritance

class Animal {

public:

    void eat() {

        cout << "eats\n";

    }

    void breathe() {

        cout << "breathes\n";

    }

};

class Mammal : public Animal {

public:

    string bloodType;

    Mammal() {

        bloodType = "warm";

    }

};

class Dog : public Mammal {

public:

    void tailWag() {

        cout << "a Dog wags its tail\n";

    }

};

int main() {

   Dog d1;

   d1.eat();

   d1.breathe();

   d1.tailWag();

   cout << d1.bloodType << endl;  //  my Mistake ->  d1.bloodType();

    return 0;

}