#include <iostream>

using namespace std;

int main()
{
    int mark;
    char grade;

    cout << "Enter your mark in the course: ";
    cin  >> mark;

    if      (mark >= 80) grade = 'A';
    else if (mark >= 70) grade = 'B';
    else if (mark >= 60) grade = 'C';
    else if (mark >= 50) grade = 'D';
    else                 grade = 'F';

    cout << "The letter grade is " << grade << endl;

    switch (grade)
    {
        case 'A': cout << "Excellent!"; break;
        case 'B': cout << "Great job!"; break;
        case 'C':
        case 'D': cout << "Good job!"; break;
        default:  cout << "Better luck next time!";
    }

    return 0;
}