if (score <= 100 && score >= 0) 
		if (score >= 70)
			if (score >= 77)
				if (score >= 87)
					if (score >= 94)
					            grade = 'A';	
					else
					  grade = 'B';
				else
					grade = 'C';
			else
				grade = 'D';
		else
			grade = 'F';
	else
                cout << "Invalid input!\n";
                cout << "Grade must be between 0 and 100!\n";