#include <bits/stdc++.h>

#define rep(i,n) for(int i=0;i<(n);++i)
#define pb push_back;

using namespace std;

typedef long long ll;

int main(){
    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];
    }
    sort(A, A + N);
    sort(B, B + N);

    int res = 0;
    int count = 0;
    do {
        int cpB[N];
        copy(B, B + N, cpB);
        do {
            int win = 0;
            for (int i = 0; i < N; i++) {
                if (A[i] > cpB[i]) win++;
            }

            if (win > N / 2) res++;
            count++;
        } while (next_permutation(cpB, cpB + N)); 
    } while(next_permutation(A, A + N));
	
	cout << (double) res / count << endl;
	
	return 0;
}