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# typed: false
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orbits = ARGF
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.read.split("\n").map {|l| l.split(?)) }
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.each.with_object(Hash.new {|h,k| h[k] = []}) {|(a, b), o|
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o[a] << b
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}
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roots = orbits.keys.select {|x| orbits.values.none? {|v| v.include?(x) }}
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depths = {}
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queue = roots.map {|x| [x, []] }
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until queue.empty?
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x, a = queue.shift
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depths[x] = a
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a = a + [x]
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queue.concat(orbits.fetch(x) { [] }.map {|y| [y, a] })
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end
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# p depths.values.map(&:size).sum
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you = depths.fetch("YOU")
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san = depths.fetch("SAN")
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p ((you + san) - (you & san)).size
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