#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;
using pll = pair<ll,ll>;

#define INF (1LL << 60)
#define MOD 1000000007
#define PI 3.14159265358979323846

#define REP(i,m,n) for(ll (i)=(m),(i_len)=(n);(i)<(i_len);++(i))
#define FORR(i,v) for(auto (i):v)
#define ALL(x) (x).begin(), (x).end()
#define PR(x) cout << (x) << endl
#define PS(x) cout << (x) << " "
#define SZ(x) ((ll)(x).size())
#define MAX(a,b) (((a)>(b))?(a):(b))
#define MIN(a,b) (((a)<(b))?(a):(b))
#define REV(x) reverse(ALL((x)))
#define ASC(x) sort(ALL((x)))
#define DESC(x) ASC((x)); REV((x))
#define pb push_back
#define eb emplace_back

int main()
{
    ll N;
    cin >> N;
    vec A(N), B(N);
    REP(i,0,N) cin >> A[i];
    REP(i,0,N) cin >> B[i];

    ll num = 0, den = 0;
    ASC(A);
    do {
        ASC(B);
        do {
            ll a = 0, b = 0;
            REP(i,0,N) {
                if(A[i] > B[i]) ++a;
                else if(A[i] < B[i]) ++b;
            }
            if(a > b) ++num;
            ++den;
        } while(next_permutation(ALL(B)));
    } while(next_permutation(ALL(A)));
    cout << setprecision(12) << (double)num / den << endl;

    return 0;
}

/*



*/