Dmitri Shostakovich typically catalogued his compositions and occasionally his arrangements of other composers' music with opus numbers. He began this practice with the early Scherzo in F-sharp minor and continued until the end of his life. Nevertheless, most of his juvenilia, unfinished works from his artistic maturity (such as the operas Orango and The Gamblers), and numerous completed works were left unnumbered. There were also instances when Shostakovich took an opus number assigned to one work, then gave it to another, or was undecided about the numbering of a finished composition. Further complicating the matter was an error he committed in compiling his own music in the 1930s. This led to his soundtracks for The Youth of Maxim and Girl Friends sharing the same opus number.