discussed Cited "see, e.g." Commonwealth v. Cintron See, e.g., United States v. Henderson, 320 F.3d 92, 103 (1st Cir.), cert. denied, 539 U.S. 936 (2003), affirming a conviction for school zone distribu tian, and citing Soler for the point that “the schoolyard statute envisions straight-line rather than pedestrian-route measurements,” where the government introduced a map that provided a detailed illustration of the distances.