#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i,k,n) for(int i = k;i < (n);i++)
typedef long long ll;
typedef pair <int,int> P;
const ll MOD = 1e9 + 7;
const int INF = 1e8;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

int main(void){
    int n;
    double gamewin = 0,matchnum = 0,ans;
    cin >> n;
    vector<int> a(n),b(n);

    rep(i,n) cin >> a.at(i);
    rep(i,n) cin >> b.at(i);
    sort(a.begin(),a.end());

    do
    {
        int win = 0;
        rep(i,n){
            if(a[i] > b[i]) win++;//カードの数で勝利
        }
        if(win > n/2) gamewin++;//試合で勝利

        matchnum++;
        
    } while (next_permutation(a.begin(),a.end()));
    
    ans = gamewin/matchnum;

    cout << ans << endl;

}