#include <bits/stdc++.h>
#include <atcoder/all>

using namespace atcoder;
using namespace std;
#define rep(i,a,b) for(int i = a; i < b; i++)
#define rrep(i,a,b) for(int i = a; i >= b; i--)
#define fore(i,a) for(auto& i : a)
#define sz(x) (int)(x).size()
using ll = long long;
using pint = pair<int, int>;
using pll = pair<long long, long long>;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
const int IINF = INT_MAX;
const long long LINF = 1LL << 60;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

int main() {
    cout << setprecision(15) << fixed;
    int N; cin >> N;
    vector<int> A(N);
    vector<int> B(N);
    rep(i, 0, N) cin >> A[i];
    rep(i, 0, N) cin >> B[i];
    vector<int> ord(N);
    iota(ord.begin(), ord.end(), 0);
    int all = 0;
    int win = 0;
    do {
        ++all;
        int a = 0;
        rep(i, 0, N) {
            if (A[ord[i]] > B[i]) ++a;
            if (A[ord[i]] < B[i]) --a;
        }
        if (a > 0) win++;
    } while(next_permutation(ord.begin(), ord.end()));
    cout << (double)win / all << endl;
    return 0;
}