day12.cpp

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

class Student{
protected:
	string firstName;
	string lastName;
	int phone;
public:
	Student(string fname, string lname, int p){
		firstName = fname;
		lastName = lname;
		phone = p;
	}
	void display(){
		cout << "First Name: " << firstName << "\nLast Name: " << lastName << "\nPhone: " << phone;

	}

};

class Grade : public Student{
public:
	~Grade(){};
	Grade(string f, string s, int p, int sc) : Student(f, s, p)  {

		score = sc;
	};

	char calculate(){
		if (score < 40)
		{
			return 'D';
		}
		else if (score < 60)
		{
			return 'B';
		}
		else if (score < 75)
		{
			return 'A';
		}
		else if (score < 90)
		{
			return 'E';
		}
		else
		{
			return 'O';
		}

	}
private:
	int score;
};
int main() {
	string firstName, lastName;
	int score, phone;
	cin >> firstName;
	cin >> lastName;
	cin >> phone;
	cin >> score;
	Student *stu = new Grade(firstName, lastName, phone, score);
	stu->display();
	Grade *g = (Grade*)stu;
	cout << "\nGrade: " << g->calculate();
	return 0;
}