The black and white team of four will go from the east bank of the river to the west bank. Now there is only one wooden boat and no boatman, and the wooden boat can only carry two people at a time; it is known that it takes 7 minutes for Ozebra to cross the river, 3 minutes for Xiaomei, 2 minutes for Ouou, and 5 minutes for Koizumi; then, how many minutes will it take at least black and white The team can safely cross the river.
黑白团队四人要从河的东岸到西岸．现在只有一条木船且无船工，木船一次最多只能载两人；已知奥斑马渡河需要7分钟，小美需要3分钟，欧欧需要2分钟，小泉需要5分钟；那么，至少需要多少分钟黑白团队都能安全的渡过河．
<gadget id="calculator">3 + 2 + 7 + 3 + 3</gadget>
<output>18</output>

<result>18</result>