#include<iostream>
#include<string>
using namespace std ;
class M {
    public :
    string name,subjects;
    int marks;
    
    void m(){
        if (name.empty() || subjects.empty()||marks<0||marks>100){
            cout<<"Invalid input";
            return;
            }
        string g ;
        if (marks >= 90 && marks<100){
            g = 'A' ;
        }
        else if (marks < 90 && marks >= 75){
             g = 'B' ;
        }
        else if (marks < 75 && marks >= 50){
             g = 'C' ;
        }
        else if (marks < 50){
            g = 'F' ;
         }
cout<<"Name: "<<name<<endl;
cout<<"subject: "<<subjects<<endl;
cout<<"Marks: "<<marks<<endl;
cout<<"Grade: "<<g<<endl;
    }    
};
int main(){
    string stu , sub ;
    
    int mk ;
    cin>>stu>>sub;
    cin>>mk;
    cin>>g;
    M s;
    s.marks = mk;
    s.name = stu;
    s.subjects = sub;
    s.m();
    
}