ex5_05.cpp

#include <iostream>
#include <vector>
#include <string>

using std::vector;
using std::string;
using std::cout;
using std::endl;
using std::cin;

int main()
{
    vector<string> scores = {"F", "D", "C", "B", "A", "A++"};

    int grade{0};
    while (cin >> grade) {
        string lettergrade;
        if (grade < 60)
            lettergrade = scores[0];
        else {
            lettergrade = scores[(grade - 50) / 10];
            if (grade != 100) {
                if (grade % 10 > 7)
                    lettergrade += "+";
                else if (grade % 10 < 3)
                    lettergrade += "-";
            }
        }

        cout << lettergrade << endl;
    }

    return 0;
}