#include <iostream>
#include <string>
using namespace std;

class Student {
    private:
    string name;
    string subject;
    int marks;
    
    public:
    Student(string n, string s, int m) {
        name = n;
        subject = s;
        marks = m;
    }
    
    void  displayGrade() {
        if (name.empty() || subject.empty() || marks < 0 || marks > 100) {
        cout << "Invlaid input";
        return;
    }
    
    char grade;
    if (marks >= 90)
    grade = 'A';
    else if (marks >= 75)
    grade = 'B'
    else if (marks >= 50)
    grade = 'C';
    else
    grade = 'F';
    
    cout << "Name: " << name << endl;
    cout << "Sunject: " << subject << endl;
    cout << "Marks: " << marks << endl;
    cout << "Grade: " << grade;
    }
};  

int main() {
    string name, subject;
    int marks;
    
    getline(cin, name);
    getline(cin, subject);
    cin >> marks;
    
    Student s(name, subject, marks);
    s.displayGrade() ;
    
    return 0;
}