import java.io.File;
import java.io.IOException;
import java.util.*;
 
public class Main {
	public static void main(String[] args) throws IOException {
		//File file = new File("input.txt");
		//Scanner sc = new Scanner(file);
		
		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();
		
		ArrayList<Integer> list = new ArrayList<Integer>();
		int[] d = dfs(list, A, B, N);
		//System.out.println(d[0] + " " + d[1] + " ");
		System.out.println((1.0 * d[0] / d[1]));
	}
	
	public static int[] dfs(ArrayList<Integer> cardIndexList, int[] A, int[] B, int N){
		int winNum = 0;
		int battleNum = 0;
		
		if(cardIndexList.size() == N){
			int count = 0;
			for(int i = 0; i < N; i++){
				//System.out.print(A[cardIndexList.get(i)]);
				if(A[cardIndexList.get(i)] > B[i]) count++;
				if(A[cardIndexList.get(i)] < B[i]) count--;
			}
			//System.out.println();
			battleNum = 1;
			if(count >= 1) winNum =  1;
			else winNum = 0;
		}else{
			for(int i = 0; i < N; i++){
				if(!cardIndexList.contains(i)){
					ArrayList<Integer> nextList = new ArrayList<Integer>();
					for(Integer m : cardIndexList) nextList.add(m);
					nextList.add(i);
					int[] d = dfs(nextList, A, B, N);
					winNum += d[0];
					battleNum += d[1];
				}
			}
		}
		
		int[] d = {winNum, battleNum};
		return d;
	}
}