#include <iostream>
#include <cmath>
#include <string>
#include <cstring>
#include <utility>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#define debug(x) cerr << #x << ':' << x << endl
#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef long long ll;

int main(){
    int n;
    cin >> n;
    vector<int> A(n), B(n);
    REP(i, n) cin >> A[i];
    REP(i, n) cin >> B[i];
    int a_win=0, b_win=0, draw=0;
    sort(ALL(A));
    sort(ALL(B));
    do{
        do{
            int a=0, b=0;
            REP(i, n){
                if(A[i]>B[i]) a++;
                else if(A[i]<B[i]) b++;
            }
            if(a>b) a_win++;
            else if(a<b) b_win++;
            else draw++;
        }while(next_permutation(ALL(B)));
    }while(next_permutation(ALL(A)));
    cout << a_win*1.0 / (a_win+b_win+draw) << endl;
    return 0;
}