At the end of the week, Xiao Wang tore off the 7-day calendar of this week. If the sum of the 7 days of this week is 63, what is the date of the last day of this week?
一周结束了，小王撕下了本周7天的日历，如果这一周7天日期数的和为63，那么这周的最后一天是多少号．
<result>12</result>