#include <iostream>

using namespace std;

​

char gradeFunction(double avg) {

  if (avg >= 90) return 'A';

  else if (avg >= 80) return 'B';

  else if (avg >= 70) return 'C';

  else if (avg >= 60) return 'D';

  else return 'F';

}

​

int main() {

  int count;

  double sum = 0, grade;

​

  cout << "How many grades (1 to 5)? ";

  cin >> count;

​

  if (count < 1 || count > 5) {

    cout << "Invalid number. You must enter between 1 and 5 grades.\n";

    return 1;

  }

​

  for (int i = 1; i <= count; i++) {

    cout << "Enter grade " << i << ": ";

    cin >> grade;

    sum += grade;

  }

​

  double avg = sum / count;

  cout << "Average: " << avg << "\n";

  cout << "Letter grade: " << gradeFunction(avg) << "\n";

​

  return 0;

}

​