#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 ;
    }
    char grade = (marks >=90) ? 'A' :(marks>=75) ? 'B' : (marks >=50) ? 'C': 'F';
         cout << "Name: " << name <<"\nSubject: " << subject<< "\nMarks: " << marks<< "\nGrade: " << grade << endl;
    }
};
int main(){
    string n, s;
    int m;
    if (getline(cin, n)&& getline(cin, s)&& getline(cin >> m)){
        student st(n, s, m);
        st.displayGrade();
    } else{
        cout << "Invalid input" << endl;
}
return 0;
}