There is a kind of mineral water that costs 3 yuan per bottle. Recently, the store has launched a "buy 3 get 1 free" promotion. There are 45 people in class 1, and each person drinks a bottle. How much do they need to spend at least?
有一种矿泉水每瓶3元，最近商店推出"买三送一"的优惠活动，三1班有45人，每人喝一瓶，他们至少需要花多少元．
<gadget id="calculator">11 * 3</gadget>
<output>33</output>

<gadget id="calculator">33 + 1</gadget>
<output>34</output>

<gadget id="calculator">3 * 34</gadget>
<output>102</output>

<result>102</result>