Task: Text Categorization
Input (English): The protagonist of this poem sees "pale Kings, and Princes too, / Pale warriors, death-pale were they all" in "the latest dream" he ever dreamt. "  He is in anguish despite the "squirrel's granary" being full and the harvest being done. This stems from his being "On the cold hill's side" after being seduced and held in the title character's thrall. FTP, name this 1819 poem that begins "O what can ail thee, Knight at arms," a poem about a cruel lady by John Keats.
Output (English): Literature