Because station A goes through five stops on the way to Miley Miley, plus Miley Miley Station A and 7 stops (pictured).

A﹉ 1﹉﹉2﹉﹉3﹉﹉4﹉﹉5﹉﹉B

Starting from point A, ***6 kinds are A 1. A2.A3.A4.A5.AB

The five types starting from 1 * * are12.13.14.15.1b.

From 2 o'clock ***4 kinds are 23.24.25.2B respectively.

Starting from 3 o'clock, * * * three kinds are 34.35.3B respectively.

From 4 o'clock * * * two kinds are 45.4B respectively.

*** 1 species is 5B from 5 o'clock.

Add a ***2 1 species.

Simple algorithm 7-1= 66+5+4+3+2+1= 21.

100% correct. I am a junior high school student. I have done this problem 1000 times.