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

typedef long long ll;
typedef pair<int, int> P;

const ll mod =  1000000007;  //出力は (ans % mod + mod) % mod  (負の剰余を正にする)
const int inf = 1e9;
const long long INF = 1LL << 60;   // INF = 1152921504606846976

int dx[4] = {-1,0,0,1};
int dy[4] = {0,-1,1,0};

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];
    sort(a.begin(),a.end());
    sort(b.begin(),b.end());
    int cnt = 0;
    int win = 0;
    do{
        int big = 0;
        cnt++;
        rep(i,n){
            if(a[i] > b[i]) big++;
        }
        if(big > n/2) win++;
    }while(next_permutation(a.begin(),a.end()));
    double ans = (double)win/(double)(cnt);
    cout << ans << endl;
}