//package Qy
import java.util.*
import java.math.*
import java.lang.Math.*
import java.nio.IntBuffer

private val readString: ()->String = {readLine()!!}
private val readInt: ()->Int = {readLine()!!.toInt()}
private val readLong: ()->Long = {readLine()!!.toLong()}
private val readIntArray: ()->IntArray = {readLine()!!.split(' ').map{it.toInt()}.toIntArray()}
private val readLongArray: ()->LongArray = {readLine()!!.split(' ').map{it.toLong()}.toLongArray()}
private val errPrintln: (String)->Unit = {msg -> System.err.println(msg)}
private val MOD = 1e9.toLong()+7
private val INF = Int.MAX_VALUE/2
private val LINF = Long.MAX_VALUE/2


private fun permutation(A: IntArray): List<IntArray> {
    val ary = A.sorted()
    val N = ary.size
    val used = BooleanArray(N){false}
    val hm = HashMap<IntBuffer, IntArray>()
    val ptn = ArrayList<Int>(0)
    fun dfs(n: Int) {
        if (n >= N) {
            val value = ptn.toIntArray()
            val key = IntBuffer.wrap(value)
            hm[key] = value
        }
        for (i in 0 until N) {
            if (used[i]) continue
            used[i] = true
            ptn.add(ary[i])
            dfs(n+1)
            ptn.removeAt(ptn.lastIndex)
            used[i] = false
        }
    }
    dfs(0)
    val res = ArrayList<IntArray>()
    for (key in hm.keys.sorted()) {
        res.add(hm[key]!!)
    }
    return res.toList()
}


private fun solveY(A: IntArray, B: IntArray): Double {
    val a = A.sorted()
    val bPatterns = permutation(B)

    var aWin = 0
    for (bPattern in bPatterns) {
        var aw = 0; var bw = 0; var draw = 0
        a.forEachIndexed { i, v ->
            if (v > bPattern[i]) aw++
            else if (v < bPattern[i]) bw++
            else draw++
        }
        if (aw > bw) aWin++
    }

    return aWin.toDouble() / bPatterns.size
}


fun main(args: Array<String>) {
    val N = readInt()
    val A = readIntArray()
    val B = readIntArray()

    val ans = solveY(A, B)

    println("%.8f".format(ans))
}