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

class Main {
	public static void main(String[] args) throws Exception {
		new Main().run();
	}
	
	void run() {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		int[] o1=new int[N];
		int[] o2=new int[N];
		for(int i=0;i<N;++i) {
			o1[i]=i;
			o2[i]=i;
		}
		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();
		}
		double num=0;
		double den=0;
		do {
			for(int i=0;i<N;++i) o1[i]=i;
			do {
				int p=0;
				for(int j=0;j<o1.length;++j) {
					if(a[o1[j]]>b[o2[j]])++p;
					else if(a[o1[j]]<b[o2[j]])--p;
				}
				if(p>0)++num;
				++den;
			}while(nextPermutation(o1));
		}while(nextPermutation(o2));
		System.out.println(num/den);
	}
	
	boolean nextPermutation(int[] o) {
		int s=o.length-1;
		while(s>0&&o[s-1]>o[s]) --s;
		if(s==0)return false;
		int p=s;
		while(p+1<o.length&&o[s-1]<o[p+1])++p;
		o[s-1]^=o[p];o[p]^=o[s-1];o[s-1]^=o[p];
		int t=o.length-1;
		while(s<t) {
			o[s]^=o[t];o[t]^=o[s];o[s]^=o[t];
			++s;--t;
		}
		return true;
	}
	
	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
	
}