package no133;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		int[] b = new int[n];
		for(int i=0;i<n;i++) {
			a[i] = sc.nextInt();
		}
		for(int i=0;i<n;i++) {
			b[i] = sc.nextInt();
		}
		int[] pa = new int[n];
		for(int i=0;i<n;i++) {
			pa[i] = i;
		}
		double ans = 0;
		do {
			int wins = 0;
			for(int i=0;i<n;i++) {
				if(a[pa[i]] > b[i]) {
					wins++;
				}
			}
			if (wins > n / 2) {
				ans++;
			}
		} while(nextPermutation(pa));
		for(int i=1;i<=n;i++) {
			ans /= i;
		}
		System.out.println(ans);

	}
	static boolean nextPermutation(int[] p) {
		for(int a=p.length-2;a>=0;--a) {
			if(p[a]<p[a+1]) {
				for(int b=p.length-1;;--b) {
					if(p[b]>p[a]) {
						int t = p[a];
						p[a] = p[b];
						p[b] = t;
						for(++a, b=p.length-1;a<b;++a,--b) {
							t = p[a];
							p[a] = p[b];
							p[b] = t;
						}
						return true;
					}
				}
			}
		}
		return false;
	}
}