SEOUL • Thirty teenagers, thousands of hours of training, dozens of shattered dreams. It all comes to a head next week when the Blitzers will be launched into the cut-throat K-pop market, hoping to become the next BTS. An all-male septet - like the musical phenomenon that topped the United States Billboard charts last year - their three years of training are being distilled into three minutes of music and dancing that will determine whether they are a hit or just another nowhere band. The routine, always intense, is punishing in the weeks running up to their debut: gym sessions, singing lessons, promotional shoots and around 10 hours of dance practice into the early morning.