// editor3
#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<<"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 name,subject;
    int marks;
    
    getline(cin,name);
    getline(cin,subject);
    cin>>marks;
    
    Student s(name,subject,marks);
    s.displayGrade();
    return 0;
}