// {{{
#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <complex>
#include <vector>
#include <list>
#include <set>
#include <queue>
#include <stack>
#include <map>
#include <string>
#include <algorithm>
#if __cplusplus >= 201103
#include <numeric>
#endif
using namespace std;

#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define FORR(i, a, b) for(int i = (a); i >= (b); i--)
#define REP(i, n) for(int i = 0; i < (n); i++)
#define REPR(i, n) for(int i = (n); i >= 0; i--)
#define ALL(x) (x).begin(), (x).end()

//#if __cplusplus >= 201103
typedef long long ll;
//#endif
typedef pair<int, int> P;
typedef pair<int, P> IP;

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

const int INF = 100000000;
//#if __cplusplus >= 201103
const ll LINF = 10000000000000000ll;
//#endif
const int MOD = 1e9 + 7;
const double EPS = 1e-9;
// }}}

int n;
int a[4];
int b[4];

void init()
{
}

void solve()
{
    int awin = 0;
    int total = 0;
    sort(a, a+n);
    do{
        sort(b, b+n);
        do{
            total += 1;
            int awin_once = 0;
            REP(i, n){
                awin_once += (a[i] > b[i] ? 1 : 0);
            }
            awin += (awin_once > n/2 ? 1 : 0);
        }while(next_permutation(b, b+n));
    }while(next_permutation(a, a+n));

    cout << (double)awin / total << endl;
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    REP(i, n) cin >> a[i];
    REP(i, n) cin >> b[i];
    solve();
    return 0;
}

// vim:set foldmethod=marker: