There are 5 activity groups in the club, the literature group has activities every 1 day, the computer group has activities every 2 days, the foreign language group has activities every 3 days, the calligraphy and painting group has activities every 4 days, and the entertainment group has activities every 5 days once. On the evening of April 1st, the five groups were active in the club at the same time, and then they followed the above-mentioned regulations without interruption. In April, May, and June, how many nights did the group have no activity?
俱乐部有5个活动小组，文学小组每隔1天活动一次，计算机小组每隔2天活动一次，外语小组每隔3天活动一次，书画小组每隔4天活动一次，文娱小组每隔5天活动一次．四月一日晚上五个小组同时在俱乐部活动，以后则按上述规定进行，从不间断．四月，五月，六月这三个月中有多少个晚上一个小组都没有活动．
<gadget id="calculator">30 - 15</gadget>
<output>15</output>

<gadget id="calculator">18 - 9</gadget>
<output>9</output>

<gadget id="calculator">90 - 45 - 15 - 9</gadget>
<output>21</output>

<gadget id="calculator">6 - 3</gadget>
<output>3</output>

<gadget id="calculator">21 + 3</gadget>
<output>24</output>

<result>24</result>