#include <iostream>
#include <cstdio>
#include <vector>
#include <map>

using namespace std;

map <vector<int>,double> a;
double p;

double calc(vector <int> aa){
    if (aa[12]){
        return 1;
    }
    if (aa[13]==6 || aa[14]==6){
        return 0;
    }
    if (a.find(aa)!=a.end()){
        return a[aa];
    }
    double ans=0;
    for (int i=0;i<13;i++){
        int j=i;
        while (aa[j]){
            j=(j+1)%13;
        }
        aa[j]=1;
        aa[13]++;
        ans+=p*calc(aa);
        aa[13]--;
        aa[14]++;
        ans+=(1-p)*calc(aa);
        aa[14]--;
        aa[j]=0;
    }
    ans/=13.0;
    a[aa]=ans;
    return ans;
}

int main(){
    vector <int> aa(15,0);
    cin>>aa[13]>>aa[14];
    for (int i=0;i<aa[13]+aa[14];i++){
        int t;
        cin>>t;
        t--;
        aa[t]=1;
    }
    cin>>p;
    if (aa[12]){
        cout<<0.0;
        return 0;
    }
    cout<<calc(aa);
    return 0;
}