Task: Question Generation
Input (English): Between Second and Third Avenues, 21st Street is alternatively known as Police Officer Anthony Sanchez Way. Along the northern perimeter of Gramercy Park, between Gramercy Park East and Gramercy Park West, 21st Street is known as Gramercy Park North.
Output (English): What is 21st Street known as along the northern perimeter of Gramercy Park?