#include <bits/stdc++.h>
#define debug(x) cerr << #x << ": " << x << '\n';
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = (int)1e9;
const int MOD = (int)1e9 + 7;

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

int main(void){
    cin >> N;
    for(int i = 0; i < N; i++) cin >> A[i];
    for(int i = 0; i < N; i++) cin >> B[i];

    int x = 0, y = 0;
    int ar[4];
    for(int i = 0; i < N; i++) ar[i] = i;

    do{
        y++;
        int win = 0, lose = 0;
        for(int i = 0; i < N; i++){
            if(A[i] > B[ar[i]]) win++;
            else lose++;
        }
        if(win > lose) x++;
    }while(next_permutation(ar, ar+N));

    // debug(x); debug(y);
    cout << setprecision(7) << (double) x / y << '\n';

    return 0;
}