#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

int main() {
    int n;
    cin >> n;
    vector<int> A(n);
    vector<int> B(n);
    rep(i, n) {
        cin >> A[i];
    }
    rep(i, n) {
        cin >> B[i];
    }
    vector<int> ind(n);
    rep(i, n) {
        ind[i] = i;
    }

    int all = 0, win = 0, a = 0; 

    do {
        a = 0;
        rep(i, n) {
            if(A[ind[i]] > B[i]) a++;
            if(A[ind[i]] < B[i]) a--;
        }
        if (a > 0) win++;
        all++;
    } while (next_permutation(ind.begin(), ind.end()));
    
    cout << (double)win/all << endl;

    return 0;
}