#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
const int MOD = int(1e9+7);

int N,M,W,H;
int res = 0;

int A[11],B[11];

int main(){
    cin >> N;
    REP(i,N) cin >> A[i];
    REP(i,N) cin >> B[i];

    int total = 0, win = 0;
    sort(A,A+N);
    do {
        sort(B,B+N);
        do {
            int c = 0, d = 0;
            for(int i = 0; i < N; i++){
                if(A[i]>B[i]) c++; else d++;
            }
            if(c > d) win++;
            total++;
        }while(next_permutation(B,B+N));
    }while(next_permutation(A,A+N));

    cout << setprecision(9) << (1.*win/total) << endl;
    return 0;
}