// Class average calculating program 

class Average {
  
  public static void main ( String[] args ) {

    double average, counter, total; // number with decimal point
    char grade;

    // initialization phase
    total = 0;
    counter = 0;

    // processing phase

    System.out.print( "Enter letter grade, Z to end: " );
    grade = Stdin.getChar();

    while (grade != 'Z') {

      if (grade == 'A') {
        total = total + 90;
      }
      else if (grade == 'B') {
        total = total + 75;
      }
      else if (grade == 'C') {
        total = total + 65;
      }
      else (grade == 'D') {
        total = total + 55;
      }

      counter = counter + 1;

      // get the next grade
      System.out.print( "Enter letter grade, Z to end: " );
      graed = Stdin.getChar();
    }
  
    // termination phase
    if (counter != 0) {
      average = total / counter;
      System.out.print( "Class average is " );
      System.out.println( average );
    }
    else {
      System.out.println( "No grades entered." );
    }
  }
}