import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.StringTokenizer;
import java.math.BigInteger;
    
public class Main{

static final InputStream in=System.in;
static final PrintWriter out=new PrintWriter(System.out);
static final int INF=Integer.MAX_VALUE/2;
static final long LINF=Long.MAX_VALUE/2;
    
public static void main(String[] args) throws IOException{
InputReader ir=new InputReader(in);
int n=ir.nextInt();
int[] a=ir.toIntArray(n);
int[] b=ir.toIntArray(n);
int res=0;
int win;
int all=fact(n);
sort(a);
do{
win=0;
for(int i=0;i<n;i++){
if(a[i]>b[i]) win++;
}
if(win>n/2) res++;
}while(next_permutation(a));
out.println((double)res/all);
out.flush();
}

public static boolean next_permutation(int[] a){
for(int i=a.length-2;i>=0;i--){
if(a[i]<a[i+1]){
for(int j=a.length-1;;j--){
if(a[i]<a[j]){
int temp=a[i]; a[i]=a[j]; a[j]=temp;
for(i++,j=a.length-1;i<j;i++,j--){
temp=a[i]; a[i]=a[j]; a[j]=temp;
}
return true;
}
}
}
}
return false;
}

public static int fact(int n){
if(n==1) return 1;
return n*fact(n-1);
}

public static void sort(int[] a){
for(int i=a.length-1;i>0;i--){
int t=(int)Math.random()*i;
int temp=a[i]; a[i]=a[t]; a[t]=temp;
}
Arrays.sort(a);
}

static class InputReader {
private InputStream in;
private byte[] buffer=new byte[1024];
private int curbuf;
private int lenbuf;

public InputReader(InputStream in) {this.in=in;}
  
public int readByte() {
if(lenbuf==-1) throw new InputMismatchException();
if(curbuf>=lenbuf){
curbuf= 0;
try{
lenbuf=in.read(buffer);
}
catch (IOException e) {
throw new InputMismatchException();
}
if(lenbuf<=0)
return -1;
}
return buffer[curbuf++];
}

public boolean isSpaceChar(int c){return !(c>=33&&c<=126);}

private int skip() {int b; while((b = readByte())!=-1&&isSpaceChar(b)); return b;}

public String next() {
int b=skip();
StringBuilder sb=new StringBuilder();
while(!isSpaceChar(b)){
sb.appendCodePoint(b);
b=readByte();
}
return sb.toString();
}
 
public int nextInt() {
int c=readByte();
while (isSpaceChar(c)) c=readByte();
boolean minus=false;
if (c=='-') {
minus=true;
c=readByte();
}
int res=0;
do{
if(c<'0'||c>'9') throw new InputMismatchException();
res=res*10+c-'0';
c=readByte();
}while(!isSpaceChar(c));
return (minus)?-res:res;
}

public long nextLong() {
int c=readByte();
while (isSpaceChar(c)) c=readByte();
boolean minus=false;
if (c=='-') {
minus=true;
c=readByte();
}
long res = 0;
do{
if(c<'0'||c>'9') throw new InputMismatchException();
res=res*10+c-'0';
c=readByte();
}while(!isSpaceChar(c));
return (minus)?-res:res;
}

public int[] toIntArray(int n){
int[] a=new int[n];
for(int i=0;i<n;i++) a[i]=nextInt();
return a;
}
}
}