#! /usr/bin/env ruby

if ARGV.length != 1
        abort("Incorrect arguments - needs input file")
elsif not File.exist? (ARGV[0])
	abort("File #{ARGV[0]} did not exist")
end

file = ARGV[0]

lines = File.open(file, "r").each_line(chomp: true)

steps = lines.first.each_char.to_a.cycle

node_lines = lines.drop(1).to_a

#first_node, _ = node_lines[0].split("=")
#first_node.strip!

nodes = node_lines.map {|line| node, rest = line.split("="); left, right = rest.split(","); [node.strip, {"L" => left.strip[1..-1], "R" => right.strip[0..-2]}]}.to_h

cur_node = "AAA"
step_count = 0

while cur_node != "ZZZ"
	step_count += 1
	cur_node = nodes[cur_node][steps.next]
end

puts step_count