#include<iostream>
using namespace std;
class student{
    string nmae,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;}