BTS' free concert at Gwanghwamun Square in March will have 15,000 invited fans, organizers said Wednesday. But how can those in Seoul without a ticket watch? The question has been raised as an estimated 260,000 people are projected to gather near the venue — more than 11 times the square’s official capacity of 18,000. For fans who were not among the 15,000 ticket holders, the concert will be broadcast live on large digital billboards installed on buildings surrounding Gwanghwamun Square, in cent