For BTS dalmajung merch the phrase written here is "흉즉대길" (Heungjeukdaegil) which is a four-character Hanja idiom meaning “misfortune immediately becomes great fortune.”
Namjoon uses this phrase in his verse for aliens :
"It goes
Let me, honey, talk about the business
Everybody know now where the K is
어디까지 가니 이런 제길
저주하니 아직? 흉즉대길"