int point;
	char grade;

	Grade() {
		point = -1;
		setGrade(point);
	}

	Grade(int p) {
		point = p;
		setGrade(point);
	}

	void setGrade(int p) {
		int rank;

		if (p < 0 || p > 100)
			grade = 'X';
		else {
			rank = p/10;

			switch (rank) {
				case 6: grade = 'C'; break;
				case 7: grade = 'B'; break;
				case 8: grade = 'A'; break;
				case 9:
				case 10: grade = 'S'; break;
				default: grade = 'D';
			}
		}
	}