#include<bits/stdc++.h>
using lint=long long;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint n;std::cin>>n;
    lint N=1ll<<n;
    std::vector<lint>a(n),b(n);
    for(lint&x:a)std::cin>>x;
    for(lint&x:b)std::cin>>x;
    std::vector<std::vector<lint>>dp(N,std::vector<lint>(n+1));
    dp.at(0).at(0)=1;
    for(lint bs=0;bs<N-1;bs++){
        lint pc=__builtin_popcount(bs);
        for(lint i=0;i<n;i++){
            if(bs>>i&1)continue;
            for(lint j=0;j<n;j++){
                dp.at(bs|1ll<<i).at(j+(a.at(pc)>b.at(i)))+=
                    dp.at(bs).at(j);
            }
        }
    }
    double ans=std::accumulate(dp.at(N-1).begin()+n/2+1,dp.at(N-1).end(),0ll);
    for(lint i=1;i<=n;i++)ans/=i;
    std::cout<<ans<<'\n';
}