At least how many children were born in February 2014 to ensure that 2 children whose birthdays are on the same day are found.
2014年2月出生的小朋友中至少有多少个，才保证找到2个生日是同一天的小朋友．
<gadget id="calculator">28 + 1</gadget>
<output>29</output>

<result>29</result>