Teacher Li bought three kinds of pens as prizes for the students, and spent a total of 25.40 yuan. Pencils are 0.40 yuan each, ballpoint pens are 1.40 yuan each, and fountain pens are 3 yuan each. Then what is the minimum sum of the three pens Mr. Li bought?
李老师买了三种笔作为学生的奖品，共花去25.40元．铅笔每支0.40元，圆珠笔每支1.40元，钢笔每支3元，那么李老师所购买的三种笔总和最少有多少支．
<gadget id="calculator">7 + 2 + 4</gadget>
<output>13</output>

<result>13</result>