#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define ALL(obj) (obj).begin(), (obj).end()
#define rALL(obj) (obj).rbegin(), (obj).rend()
using ll = long long;

const int dx[4] = { 1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const int INF = 1 << 30;
const int mod = 1e9+7;
vector<vector<bool>> a;

int main() {
    int N;
    cin >> N;
    vector<int> A(N);
    for (int i = 0; i < N; i++) cin >> A[i];
    vector<int> B(N);
    for (int i = 0; i < N; i++) cin >> B[i];
    
    vector<int> ca(N);
    iota(ALL(ca), 0);

    int awin = 0, cnt = 0;
    do {
        int win = 0;
        for (int i = 0; i < N; i++) {
            if(A[ca[i]] > B[i]) win++;
            else win--;
        }
        if(win > 0) awin++;
        cnt++;
    } while(next_permutation(ALL(ca)));

    double ans;
    ans = 1.0* awin / cnt;
    printf("%.3lf\n", ans);
    return 0;
}