If an integer is combined with the three numbers 1, 2, and 3 to form a formula through addition, subtraction, multiplication, and division (you can add parentheses), and the result is equal to 24, then this integer is called usable. So, among the seven numbers 4, 5, 6, (7, 8, 9, 10, how many numbers are available?
如果一个整数，与1，2，3这三个数，通过加减乘除运算(可以添括号)组成算式，结果等于24，那么这个整数就称为可用的．那么，在4，5，6，(7，8，9，10这七个数中，可用的数有多少个．
<result>7</result>