#include <bits/stdc++.h>
#define rep(i, n) for (int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
const ll MOD = 1000000007;
const ll INF = 10000000000000000;
vector<int> x4 = {0, 1, 0, -1}, x8 = {0, 1, 1, 1, 0, -1, -1, -1};
vector<int> y4 = {1, 0, -1, 0}, y8 = {1, 1, 0, -1, -1, -1, 0, 1};
template<class T> struct edge { int from, to; T cost;};
template<class T> inline bool chmin(T& a, T b){if (a>b){a = b; return true;}return false;}
template<class T> inline bool chmax(T& a, T b){if (a<b){a = b; return true;}return false;}
template<class T> inline T powerM(T a,T b){if (b==0) return 1;
T tmp = powerM(a,b/2); if (b%2==0) return tmp*tmp%MOD; else return tmp*tmp%MOD*a%MOD; }
template<class T> inline T power(T a,T b,T m){ if (b==0) return 1;
  T tmp = power(a,b/2,m); if (b%2==0) return tmp*tmp%m; else return tmp*tmp%m*a%m; }
template<class T> inline T gcd(T a, T b){if (b==0) return a; return gcd(b, a%b);}
template<class T> inline T lcm(T a, T b){return a / gcd(a,b) * b;}
// ax+by=gcd(a,b)を解く
template<class T> inline T extgcd(T a,T b,T &x,T &y){if (b==0){x=1; y=0; return a;} T d=extgcd(b,a%b,y,x); y -= a/b*x; return d;}


int main() {
  int n; cin >>n;
  vector<int> a(n),b(n);
  rep(i, n) cin >>a.at(i);
  rep(i, n) cin >>b.at(i);
  int win = 0;
  int games = 0;
  vector<int> v(n);
  rep(i, n) v[i] = i;
  sort(all(v));
  do {
    int awin = 0; int bwin = 0;
    for (int i=0; i<n; i++){
      int carda = a[v[i]], cardb = b[i];
      if (carda > cardb) awin++;
      if (carda < cardb) bwin++;
    }
    games++;
    if (awin > bwin) win++;
  } while (next_permutation(all(v)));
  double res = (double)win / (double)games;
  cout <<res <<endl;
}