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

int main(){
    int n; cin >> n;
    int a[n], b[n];
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    sort(a, a+n);
    sort(b, b+n);

    int ans = 0;
    int cnt = 0;
    do{
        do{
            int awin = 0;
            int bwin = 0;
            rep(j, n){
                if(a[j] > b[j]) awin++;
                else if(a[j] < b[j]) bwin++;
            }
            if(awin > bwin) ans++;
            cnt++;
        }while(next_permutation(b, b+n));
    }while(next_permutation(a, a+n));
    int nn = 1;
    rep(i, n) nn *= (i+1);
    cout << (double(ans)/(nn*nn)) << endl;


    return 0;
}