#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n;
    cin >> n;

    int a[n], b[n];
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];

    double ans = 0;

    const int N = n;
    vector<int> v(N);
    iota(v.begin(), v.end(), 0);       // v に 0, 1, 2, ... N-1 を設定
    do {
        vector<int> u(N);
        iota(u.begin(), u.end(), 0);
        do{
            int x = 0, y = 0;
            rep(i,N){
                if(a[v[i]] > b[u[i]]) x++;
                else if(a[v[i]] < b[u[i]]) y++;
            }
            if(x > y) ans += 1;
        }while(next_permutation(u.begin(), u.end()));
    } while( next_permutation(v.begin(), v.end()) );     // 次の順列を生成
    
    srep(i,1,n+1) ans /= i;

    cout << ans << endl;
    return 0;
}