LG2473

#include<bits/stdc++.h>

using namespace std;

#define gc c=getchar()
#define r(x) read(x)
#define ll long lon

template<typename T>
inline void read(T&x){
    T k=1;char gc;x=0;
    while(!isdigit(c)){if(c=='-')k=-1;gc;}
    while(isdigit(c))x=x*10+c-'0',gc;x*=k;
}

const int N=(1<<15)|7;

int a[20];
int sta[N];
double f[105][N];

int main(){
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);
    int m,n;r(m),r(n);
    for(int i=1,x;i<=n;++i){
        r(a[i]);
        for(r(x);x;r(x))sta[i]|=1<<(x-1);
    }
    for(int i=m-1;~i;--i){
        for(int j=0;j<1<<n;++j){
            for(int k=1;k<=n;++k){
                if((j|sta[k])==j){
                    f[i][j]+=max(f[i+1][j],f[i+1][j|(1<<(k-1))]+a[k]);
                }
                else f[i][j]+=f[i+1][j];
            }
            f[i][j]/=n;
        }
    }
    printf("%.6lf",f[0][0]);
}