In the Problem Shell Game, they give the answer as

read = open("")

n = int(read.readline())

# shell_at_pos[i] stores the label of the shell located at position i
# The shells can be placed arbitrarily at the start.
shell_at_pos = [i for i in range(3)]

# counter[i] stores the number of times the shell with label i was picked
counter = [0 for _ in range(3)]

for _ in range(n):
	# Zero indexing: offset all positions by 1
	a, b, g = [int(i) - 1 for i in read.readline().split()]

	# Perform Bessie's swapping operation
	shell_at_pos[a], shell_at_pos[b] = shell_at_pos[b], shell_at_pos[a]

	# Count the number of times Elsie guesses each particular shell
	counter[shell_at_pos[g]] += 1

print(max(counter), file=open("shell.out", "w"))

I do not understand what the
read = open("")
line means in the code. Was it a file I was supposed to download?

It’s the input file.