5 students lined up to take pictures, among them A and B are not lined up together, how many ways are there in total?
5个同学排成一排照相，其中A、B两个人不排在一起，共有多少种排法．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">5 * 4 * 3 * 2 * 1</gadget>
<output>120</output>

<gadget id="calculator">2 * 1 * 4 * 3 * 2 * 1</gadget>
<output>48</output>

<gadget id="calculator">120 - 48</gadget>
<output>72</output>

<result>72</result>