#include<iostream>
using namespace std;

class Student {
    string name,subjcet;
    int marks;
    
public:
    Student(string n, string s,int m) {
        name=n;subject=s;marks=m;
    }
    void displayGrade() {
        if(name =="" || subjcet =="" || marks < 0 || marks>100) {
            cout << "Invalid 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 << "Subject: " << subject << endl;
        cout << "Marks: " << marks << endl;
        cout << "Grade: " << grade;
    }
};

int main() {
    string n,s;
    int m;
    cin >> n >>s >> m;
    Student obj(n,s,m);
    obj.displayGrade();
}