Students in class 4 and 1 need to subscribe to four kinds of newspapers, and each person subscribes to at least one kind, so how many subscription methods does each person have?
四1班同学们要订四种报纸，每人至少订一种，那么每人有多少种订阅方式．
<gadget id="calculator">4 + 6 + 4 + 1</gadget>
<output>15</output>

<result>15</result>