MIT Mystery Hunt 2020/Magic Railway

Magic Railway is a conundrum from the round of the 2020 MIT Mystery Hunt, flavored around a magical train ride.

Solve Path
You are told the instructions, and simply have to follow them.

For this walkthrough, each person will be noted using their initials.

The train will be represented as this table, with seats numbered as follows:

Ticket Distribution


 * JJ doesn't take a ticket and takes seat number 1.
 * UM and DM cut the line and take the only two tickets with sequential seat numbers (9/10). DM takes the higher ticket number (10).
 * AN responds to this by using magic to grab the only ticket with an odd seat number (7).
 * EPC notes this disturbance, grabs ticket number 2, and hands RR the one ticket remaining (12).
 * PO sees RR get seat 12 and conjures a fake ticket for seat number 13.

Departure


 * 1) JJ - Everyone is seated. JJ collects tickets (incrementing AN's counter as he passes by seat 7) until he finds PO at seat 13 with the fake ticket.
 * 2) PO - Conductor doesn't take fake tickets. PO uses magic to force the conductor back to seat 1 (incrementing AN's counter as he passes by seat 7). Every real ticket is dropped beneath seat 14.
 * 3) EPC - Magic was cast on the train. EPC moves to seat 14 (incrementing AN's counter as he passes by seat 7). JJ announces Arisaig.
 * 4) RR - The front seat on your side of the train opens up. RR moves to seat 2 (incrementing AN's counter as she passes by seat 7) and sings.
 * 5) AN - Someone sang. AN claps loudly and mentions a great view of a car outside his window.
 * 6) DM - Someone mentioned a great view. DM asks UM to trade seats, "please, please, pretty please". JJ announces Mallaig.
 * 7) UM - DM asked to trade seats and said please. UM and DM trade seats.
 * 8) AN - A house elf is in the seat behind you. AN moves to seat 8.
 * 9) PO - More people are sitting in even-numbered seats. PO leaves the train (incrementing AN's counter in the process) at the earliest opportunity—which is to say, right now, as JJ announces Loch Pother directly after this action.
 * 10) EPC - A suspected magic user just left the train. EPC also leaves.
 * 11) UM - The back seats are both unoccupied. UM drops the newspaper under seat 10 and tells DM to go to the back.
 * 12) DM - UM orders you to move. DM and UM move to seats 13 and 14, respectively. JJ announces Witchdale.
 * 13) RR - The train has just left Witchdale. RR wants to sing.
 * 14) JJ - Someone threatens to sing for the second time. JJ escorts RR to seat 11 and then walks back to seat 1 (incrementing AN's counter three times, to a total of 8).
 * 15) AN - The Commotion Count reaches 8. Everyone moves across the aisle. JJ announces Glencragenshire.
 * 16) DM - You see things under your seat. DM collects the tickets, crosses out every 1 and 6, then adds up the remainder and indexes [8, 6, 7, 5, 3] into GLENCRAGENSHIRE. This generates the word GRACE.
 * 17) RR - You see a house elf examining "trash". Indexing as described by the instruction yields UNDER.
 * 18) UM - The train is about to arrive at Pigsbrew Village. Name an element that goes well with the other answers. JJ announces Pigsbrew Village.

End

Puzzle Elements
Conundrum - The puzzle simply consists of following the instructions as they come up.

Red Herring - Like any conundrum, this puzzle has multiple distractor instructions to avoid short-circuiting.

Indexing - The extraction instructions explicitly ask to take indices into numerous strings.