#include <bits/stdc++.h>
using namespace std;

int main() {
    
    // 1. 入力情報取得.
    int N;
    cin >> N;
    int A[N], B[N];
    for(int i = 0; i < N; i++) cin >> A[i];
    for(int i = 0; i < N; i++) cin >> B[i];
    
    // 2. sort.
    sort(A, A + N);
    sort(B, B + N);
    
    // 3. A, B の 順列を保存.
    vector<vector<int>> va, vb;
    do{
        vector<int> v;
        for(int i = 0; i < N; ++i) v.push_back(A[i]);
        va.push_back(v);
    }while(next_permutation(A, A + N));
    
    do{
        vector<int> v;
        for(int i = 0; i < N; ++i) v.push_back(B[i]);
        vb.push_back(v);
    }while(next_permutation(B, B + N));
    
    // 4. A君が勝つ確率は？
    int counter = 0, win = 0;
    for(auto &a : va){
        for(auto &b : vb){
            int aWin = 0;
            for(int i = 0; i < N; i++) if(a[i] > b[i]) aWin++;
            if(aWin > N / 2) win++;
            counter++;
        }
    }
    
    // 5. 出力.
    double ans = (win + 0.0) / counter;
    cout << fixed << setprecision(10) << ans << endl;
    return 0;
    
}