import java.util.Arrays;
import java.util.Scanner;

public class Main {
	static int[][] list;
	static int index = 0;
	static int N;
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		N = scan.nextInt();
		int []A = new int[N];
		int []B = new int[N];

		for(int i = 0; i < N; i++) {
			A[i] = scan.nextInt();
		}
		for(int i = 0; i < N; i++) {
			B[i] = scan.nextInt();
		}
		scan.close();
		int l = fact(N);
		list = new int[l][N];
		int []a = new int[N];
		perm(0, a, new boolean[N + 1]);

		Arrays.fill(a, 0);
		int n = 100000;
		int win = 0;
		for(int i = 0; i < n; i++) {
			int t1 = (int)(Math.random() * l);
			int t2 = (int)(Math.random() * l);
			int cnt1 = 0;
			int cnt2 = 0;
			for(int j = 0; j < N; j++) {
				int c1 = A[list[t1][j] - 1];
				int c2 = B[list[t2][j] - 1];
				if(c1 > c2) {
					cnt1 ++;
				}else if(c1 < c2) {
					cnt2 ++;
				}
			}
			if(cnt1 > cnt2) {
				win ++;
			}
		}

		double ans = (double) win / n;
		System.out.println(ans);

	}
	static void perm(int n, int[] a, boolean[] flag) {
        if(n == a.length) {
        	for(int i = 0; i < N; i++) {
        		list[index][i] = a[i];
        	}
        	index ++;
            return;
        }
        for(int i = 1; i <= a.length; i++) {
            if(flag[i]) continue;
            a[n] = i;
            flag[i] = true;
            perm(n + 1, a, flag);
            flag[i] = false;
        }
    }
	static int fact(int n) {
		if(n == 1) {
			return 1;
		}else {
			return n * fact(n - 1);
		}
	}
}