#include <bits/stdc++.h>
#define ll long long
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define rev(i,n) for(int i=n-1;i>=0;i--)
#define vi vector<int>
#define vv vector<vi>
#define pb push_back
#define pi pair<int,int>
#define vp vector<pair<int,int> >
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define INF 1000000000
#define eps 1e-7
#define mod 1000000007
#define int ll
using namespace std;

int N;
int A[4], B[4];

signed main(void) {
    cin>>N;
    rep(i,N) cin>>A[i];
    rep(i,N) cin>>B[i];
    sort(A,A+N); sort(B,B+N);
    int cnt=0, all=0;
    do {
        do {
            int won=0, lost=0;
            rep(i, N) {
                if(A[i]>B[i]) won++;
                else lost++;
            }
            cerr << "won:" << won << ",lost:" << lost << endl;
            if (won>lost) cnt++;
            all++;
        } while(next_permutation(B,B+N));
    } while(next_permutation(A,A+N));
    cerr << cnt << "," << all << endl;
    cout << (double)cnt/all << endl;
    return 0;
}