Adult tickets for the museum are 5 yuan each. If you buy two adult tickets, you can get a child ticket for free. Each child ticket is 4 yuan. There are currently 3 teachers and 14 children coming to visit. How much is the minimum cost?
博物馆成人门票每张5元，买两张成人票可免费送一张儿童票，儿童票每张4元，现有3名老师和14名小朋友来参观，最少要花多少元？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">5 * 1</gadget>
<output>5</output>

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<gadget id="calculator">13 * 4</gadget>
<output>52</output>

<gadget id="calculator">10 + 5 + 52</gadget>
<output>67</output>

<result>67</result>