/**************************************************************

     Problem: 1076

     User: Tunix

     Language: C++

     Result: Accepted

     Time:1336 ms

     Memory:52984 kb

 ****************************************************************/

 //BZOJ 1076

 #include<cstdio>

 #include<cstdlib>

 #include<cstring>

 #include<iostream>

 #include<algorithm>

 #define rep(i,n) for(int i=0;i<n;++i)

 #define F(i,j,n) for(int i=j;i<=n;++i)

 #define D(i,j,n) for(int i=j;i>=n;--i)

 using namespace std;

 int getint(){

     int v=,sign=; char ch=getchar();

     while(ch<''||ch>'') {if (ch=='-') sign=-; ch=getchar();}

     while(ch>=''&&ch<='') {v=v*+ch-''; ch=getchar();}

     return v*=sign;

 }

 /*******************tamplate********************/

 const int N=,M=(<<);

 double f[N][M];

 int w[],d[],n,K;

 int main(){

 //  freopen("input.txt","r",stdin);

     K=getint(); n=getint();

     int t;

     F(i,,n){

         w[i]=getint();

         t=getint();

         while(t){ d[i]|=<<(t-); t=getint();}

     }

     D(i,K,)

         rep(j,<<n){

             F(k,,n)

                 if ( (d[k]&j)==d[k] )

                     f[i][j]+=max(f[i+][j],f[i+][j|(<<(k-))]+w[k]);

                 else f[i][j]+=f[i+][j];

             f[i][j]/=n;

         }

     printf("%.6lf",f[][]);

     return ;

 }