In the fourth grade of Yangcun Primary School, there is a mathematics test. There are 15 questions in the test. If Xiao Xixi, Xiao Feibo, Xiao Meimei, and Xiao Lanlan all answer correctly 11, 12, 13, and 14 respectively, then There are at least how many questions that all four of them answered correctly.
羊村小学四年级进行一次数学测验，测验共有15道题，如果小喜喜、小沸沸、小美美、小懒懒都答对的题目分别是11道、12道、13道、14道，那么他们四人都答对的题目最少有多少道．
<gadget id="calculator">4 + 3 + 2 + 1</gadget>
<output>10</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<result>5</result>