Something

	if (score < 70 && score >= 0) 		if (score >= 70 && score <= 76)			if (score >= 77 && score <= 86)				if (score >= 87 && score >= 78)					if (score >= 94 && score <= 100)						if (score < 0 || score > 100)							cout << "Grade must be between 0 and 100!\n";						else							cout << "Invalid input!\n";					else					  grade = 'A';				else					grade = 'B';			else				grade = 'C';		else			grade = 'D';	else		grade = 'F';