#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 displayGrad(){
        if (name.empty() || subject.empty() || marks < 0 || marks > 100) {
            cout << "Invalid input" << endl;
            return ;
    }
    string grade;
    if (marks >= 90) grade= "A";
    else if (marks >= 75) grade="B";
    else if (marks >= 50) grade="C";
    else grade ="F";
    
         cout<<"Name: "<<name<<"\n";
         cout<<"Subject: "<<subject<<"\n";
         cout<<"Marks: "<<marks<<"\n";
         cout<<"Grade: "<<grade<<endl;
    }
};
int main(){
    string n, s;
    int m;
    if (!getline(cin >> ws, n))
    return 0;
    if (!getline(cin >> ws, s))
    return 0;
    if (!(cin >>m)) 
    return 0;{
        student st(n,s,m);
        st.displayGrad ();
    }
    else{
        cout << "Invalid input" << endl;
}
return 0;
}