#include "bits/stdc++.h"
#define REP(i,n,N) for(ll i=(n); i<(N); i++)
#define RREP(i,n,N) for(ll i=(N-1); i>=n; i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define ALL(v) (v).begin(),(v).end()
#define p(s) cout<<(s)<<endl
#define p2(a,b) cout<<(a)<<" "<<(b)<<endl
typedef long long ll;
using namespace std;
const ll inf=LONG_LONG_MAX;


int N;

int main(){
    while(cin>>N){
        int A[10],B[10];
        double ans=1;
        REP(i,0,N){
            cin>>A[i];
        }
        REP(i,0,N){
            cin>>B[i];
        }
        double win=0;
        sort(A,A+N);
        do{
            int a=0;
            REP(i,0,N){
                if(A[i]>B[i]) a++;
            }
            if(a>N/2){
                win++;
            }
        }while(next_permutation(A,A+N));
        REP(i,1,N+1){
            win/=i;
        }
        printf("%.3lf\n", win);
    }

    return 0;
}