#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(marks<0||marks>100){
            cout<<"Invalid input"<<endl;
            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<<endl;
    }
};
int main()
{
    string name,subject;
    int marks;
    getline(cin,name);
    grtline(cin,subject);
    cin>>marks;
    cin.ignore(numeric_limits<<streamsize>::max(),'\n');
    if(name.empty()||subject.empty()){
        cout<<"Invalid input"<<endl;
    }else{
        student student(name,subject,marks);
        student.displaygrade();
    }
    return 0;
}