How many cases are there to select two numbers from the four numbers l, 2, 3, and 4 to form a two-digit number?
从l、2、3、4这4个数字中选出两个数组成两位数，有多少种情况．
<gadget id="calculator">3 + 3 + 3 + 3</gadget>
<output>12</output>

<result>12</result>