#include <bits/stdc++.h>
#include <regex>
#ifdef _DEBUG
#include "debug.h"
#endif
//#define int ll
#define float double
#define FOR(i, s, e) for (int i = int(s); i < int(e); ++i)
#define REP(i, e) FOR(i, 0, e)
#define all(v) (v).begin(),(v).end()
#define mkpr make_pair
#define mktp make_tuple
#define tv(tp, i) get<(i)>(tp)
#define CLEAR(obj) obj = decltype(obj)()
#define var auto
#define OUT(type) type &
#define IN(type) const type &
#define self (*this)
#define in :
#define True true
#define False false
using namespace std; using int32 = int32_t; using ll = long long; using ull = unsigned long long;
using vi = vector<int>; using vvi = vector<vi>; using vl = vector<ll>; using vvl = vector<vl>;
using vb = vector<bool>; using vvb = vector<vb>; using vc = vector<char>; using vvc = vector<vc>;
using vf = vector<float>; using vvf = vector<vf>; using vd = vector<double>; using vvd = vector<vd>;
using str = string; using vs = vector<string>;
using pii = pair<int, int>; using pll = pair<ll, ll>; using pff = pair<float, float>; using pdd = pair<double, double>;
using psl = pair<string, ll>; using tiii = tuple<int, int, int>; using tlll = tuple<ll, ll, ll>;
static const int MGN = 10; static const int ARYSZ_MAX = (int)1e7; static const ll LINF = LLONG_MAX/2;
#ifdef int
static const int INF = LINF;
#else
static const int INF = INT_MAX/2;
#endif
static double EPS = 1e-9;
#define FASTCIN() cin.tie(0);ios::sync_with_stdio(false);
#ifdef IMPORT_SAMPLE
#define DEBUG_IMPORT(file) vs args(argv, argv+argc);str sample = make_sample(args, file);ifstream ifs(sample); cin.rdbuf(ifs.rdbuf());
#else
#define DEBUG_IMPORT(file)
#endif
static inline int ord(char c) {return (int)c;}
static inline char chr(int n) {return (char)n;}
static inline bool DBLEQ(double a, double b) {return abs(a - b) < EPS;}
static inline void EPR(str msg) {cerr << msg << endl;}
static inline void AST(bool exp, str msg) {if(!exp){EPR(msg);} assert(exp);}
static inline void TAST(bool exp, str msg) {if(!exp){EPR(msg);} while(!exp){}}


void permutation(OUT(vvi) perm, IN(vi) A){
    vi a = A;
    sort(a.begin(), a.end());
    do {
        vi pt;
        for (int i : a) pt.push_back(i);
        perm.push_back(pt);
    } while (next_permutation(a.begin(), a.end()));
}


int32 main(int32 argc, char* argv[]) {
    FASTCIN();
    DEBUG_IMPORT("sample-1");


    int N; cin>>N;
    vi A(N); REP(i,N) cin>>A[i];
    vi B(N); REP(i,N) cin>>B[i];

    vvi permA;
    permutation(permA, A);
    vvi permB;
    permutation(permB, B);

    int all = permA.size() * permB.size();
    //EPR("all: " + to_string(all));

    int winA = 0;
    for (vi pa in permA) {
        for (vi pb in permB) {
            int wa = 0, wb = 0;
            REP(i,N)
                if (pa[i] > pb[i])
                    wa += 1;
                else if (pa[i] < pb[i])
                    wb += 1;

            if (wa > wb) winA += 1;
        }
    }
    //EPR("winA: " + to_string(winA));

    double ans = winA/(double)all;
    //cout << ans << endl;
    printf("%.6lf", ans);


    return 0;
}