#include<cstdio>

#include<algorithm>

using namespace std;

const int maxn = 20;

double f[102][1 << maxn];

int score[maxn], state[maxn], pos[maxn],n, m, tmp ;

int main(){

    for(int i = 1;i <= 16; ++i) pos[i] = (1 << (i - 1));

    scanf("%d%d",&n,&m);

    for(int i = 1;i <= m; ++i)

    {

        scanf("%d%d",&score[i],&tmp);

        while(tmp){ state[i] += pos[tmp]; scanf("%d",&tmp); }

    }

    for(int i = n;i >= 1; --i)

        for(int j = 0;j <= pos[m + 1]; ++j)

        {

            for(int k = 1;k <= m; ++k)

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

                    f[i][j] += max(f[i+1][j], f[i+1][j|pos[k]] + score[k]);

                else  f[i][j] += f[i + 1][j];

            f[i][j] /= m;

        }

    printf("%.6lf",f[1][0]);

    return 0;

}