The lambs play a house-to-house game. There is one extra lamb in a group of five, and one extra lamb in a group of three. How many lambs are there at least in this group?
小羊们玩过家家的游戏，5只一组多1只，3只一组也多1只，这群小羊至少有多少只？
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<result>18</result>