network().let { network ->
    network.map { (first, connected) ->
        buildSet {
            val visited = mutableSetOf<String>()
            for (sub in connected) {
                add((setOf(first, sub) + buildSet {
                    for (next in connected - visited) {
                        if (all { next in network[it].orEmpty() }) add(next)
                    }
                }).also { visited += it })
            }
        }
    }.flatten().maxBy { it.size }.joinToString(",")