Task: Question Answering
Input (English): Passage: The Five was among the myriad of subjects Tchaikovsky discussed with his benefactress, Nadezhda von Meck. By January 1878, when he wrote to Mrs. von Meck about its members, he had drifted far from their musical world and ideals. In addition, The Five's finest days had long passed. Despite considerable effort in writing operas and songs, Cui had become better known as a critic than as a composer, and even his critical efforts competed for time with his career as an army engineer and expert in the science of fortification. Balakirev had withdrawn completely from the musical scene, Mussorgsky was sinking ever deeper into alcoholism, and Borodin's creative activities increasingly took a back seat to his official duties as a professor of chemistry.
Only Rimsky-Korsakov actively pursued a full-time musical career, and he was under increasing fire from his fellow nationalists for much the same reason as Tchaikovsky had been. Like Tchaikovsky, Rimsky-Korsakov had found that, for his own artistic growth to continue unabated, he had to study and master Western classical forms and techniques. Borodin called it "apostasy", adding, "Many are grieved at present by the fact that Korsakov has turned back, has thrown himself into a study of musical antiquity. I do not bemoan it. It is understandable...." Mussorgsky was harsher: "[T]he mighty kuchka had degenerated into soulless traitors."Tchaikovsky's analysis of each of The Five was unsparing. While at least some of his observations may seem distorted and prejudiced, he also mentions some details which ring clear and true. His diagnosis of Rimsky-Korsakov's creative crisis is very accurate. He also calls Mussorgsky the most gifted musically of the Five, though Tchaikovsky could not appreciate the forms Mussorgsky's originality took. Nonetheless, he badly underestimates Borodin's technique and gives Balakirev far less than his full due—all the more telling in light of Balakirev's help in conceiving and shaping Romeo and Juliet.Tchaikovsky wrote to Nadezhda von Meck that all of the kuchka were talented but also "infected to the core" with conceit and "a purely dilettantish confidence in their superiority." He went into some detail about Rimsky-Korsakov's epiphany and turnaround regarding musical training, and his efforts to remedy this situation for himself. Tchaikovsky then called Cui "a talented dilettante" whose music "has no originality, but is clever and graceful"; Borodin a man who "has talent, even a strong one, but it has perished through neglect ... and his technique is so weak that he cannot write a single line [of music] without outside help"; Mussorgsky "a hopeless case", superior in talent but "narrow-minded, devoid of any urge towards self-perfection"; and Balakirev as one with "enormous talent" yet who had also "done much harm" as "the general inventor of all the theories of this strange group". 
Question: What is the name of the person whose diagnosis of Rimsky-Korsakov's creative crisis is very accurate?
Output (English): Tchaikovsky.