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

class student{
    string name, 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;
         }
         cout << "Name: " << name <<endl;
         cout << "Subject: " << subject <<endl;
         cout << "Marks: " << marks <<endl;
         if(marks >= 90)
            cout <<"Grade: A";
         else if (marks >=75)
             cout << "Grade:B";
         else if (marks >=50)
              cout <<"Grade: c";
         else
              cout <<"Grade:F";
     }
};
int main(){
    string name, subject;
    int marks
    getline(cin,name);
    getline(cin, subject);
    cin >> marks
    student s(name, subject,marks);
    s.displayGrade();
    return 0;
}