There are 56 students in the fifth grade experimental class of Duosi Primary School. In a mathematics test, the highest score is 95 points, and the lowest score is 78 points. Then at least how many students must be randomly selected in the class to ensure that 4 students with the same grade can be selected from them.
多思小学五年级实验班的学生有56人．在一次数学考试中，最高分是95分，最低分是78分．那么在该班中至少要任意选出多少位同学，才能保证可以从中挑出4个成绩相同的学生．
<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<gadget id="calculator">54 + 1</gadget>
<output>55</output>

<result>55</result>