#include<bits/stdc++.h>
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<iomanip>
#include<cstring>
#include<vector>
#include<cstdio>
#include<string>
#include<bitset>
#include<cmath>
#include<queue>
#include<stack>
#include<map>
#include<set>
#define mp make_pair
#define pb push_back
#define RG register
#define il inline
using namespace std;
const int mod=1e9+7;
const int N=16;
const double eps=1e-10;
typedef unsigned long long ull;
typedef vector<int>VI;
typedef long long ll;
typedef double dd;
il ll read(){
    RG ll data=0,w=1;RG char ch=getchar();
    while(ch!=‘-‘&&(ch<‘0‘||ch>‘9‘))ch=getchar();
    if(ch==‘-‘)w=-1,ch=getchar();
    while(ch<=‘9‘&&ch>=‘0‘)data=data*10+ch-48,ch=getchar();
    return data*w;
}

dd f[105][65537];
int k,n,p[N],need[N][N],g[65537];
bool check[65537];

il bool pd(int x){//判断一个状态是否为合法状态
    for(RG int i=1;i<=n;i++)
        if((x&(1<<(i-1)))==(1<<(i-1)))
            for(RG int j=1;j<=need[i][0];j++)
                if((x&(1<<(need[i][j]-1)))!=(1<<(need[i][j]-1)))
                    return 0;
    return 1;
}

il void DP(){       
    for(RG int i=k;i;i--)
        for(RG int j=1,x=g[j];j<=g[0];j++,x=g[j]){
            for(RG int a=1;a<=n;a++){
                if(check[x|(1<<(a-1))]&&f[i+1][x|(1<<(a-1))]+p[a]>f[i+1][x]){
                    //在选择合法的情况下,吃掉更优
                    f[i][x]+=f[i+1][x|(1<<(a-1))]+p[a];
                }
                else f[i][x]+=f[i+1][x];//不能吃或不吃更优
            }
            f[i][x]/=n;
        }
}

int main()
{
    k=read();n=read();
    for(RG int i=1,x;i<=n;i++){
        p[i]=read();
        while(x=read())need[i][++need[i][0]]=x;
    }

    for(RG int i=0;i<(1<<n);i++)
        if(check[i]=pd(i))g[++g[0]]=i;
    //预处理出所有合法状态

    DP();
    
    printf("%.6lf\n",f[1][0]);
    return 0;
}