// program to collect marks and output grade boundary
#include <iostream>
#include <vector>

int main()
{

        std::vector<int> grade_a;
        std::vector<int> grade_b;
        std::vector<int> grade_c;
        std::vector<int> grade_d;
        std::vector<int> grade_e;
        const int numbers(20);
        int x(numbers);

        while (x > 0) {
                int score(0);
                std::cout << "Input a mark (0-100) \n";
                std::cin >> score;

                if (score >=0 and score <= 20) {
                        std::cout << "This is a E score \n";
                        grade_e.push_back(score);
                }
                if (score > 20 and score <= 40) {
                        std::cout << "This is a D score \n";
                        grade_d.push_back(score);
                }
                if (score > 40 and score <= 60) {
                        std::cout << "This is a C score \n";
                        grade_c.push_back(score);
                }

                if (score > 60 and score <= 80) {
                        std::cout << "This is a B score \n";
                        grade_b.push_back(score);
                }
                if (score > 80 and score <= 100) {
                        std::cout << "This is a A score \n";
                        grade_a.push_back(score);
                }
                --x;
        }

        std::cout << "The grade categories for these students were as follows: \n";
        std::cout << grade_a.size() << " achieved A grade. \n";
        std::cout << grade_b.size() << " achieved B grade. \n";
        std::cout << grade_c.size() << " achieved C grade. \n";
        std::cout << grade_d.size() << " achieved D grade. \n";
        std::cout << grade_e.size() << " achieved E grade. \n";

}