#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <cmath>
#include <sstream>
#include <iomanip>
#include <queue>
#include <ctime>
using namespace std;
template <class T> void checkmin(T &t,T x){if (x < t) t = x;}
template <class T> void checkmax(T &t,T x){if (x > t) t = x;}
template <class T> void _checkmin(T &t, T x){if (t == -1) t = x; if (x < t) t = x;}
template <class T> void _checkmax(T &t, T x){if (t == -1) t = x; if (x > t) t = x;}
typedef pair <int,int> PII;
typedef pair <double,double> PDD;
typedef long long lld;
#define foreach(it,v) for (__typeof((v).begin()) it = (v).begin();it != (v).end();it++)
#define DEBUG(a) cout << #a" = " << (a) << endl;
#define DEBUGARR(a, n) for (int i = 0; i < (n); i++) { cout << #a"[" << i << "] = " << (a)[i] << endl; }
#define maxn 100000
#define oo 20000
int f[maxn][3],son[maxn][4],trup[maxn];
void calc(int now,int fa){
    int L = -1,R = -1;

    if (trup[now]){
        f[now][0] = oo,f[now][1] = 0;
        f[now][2] = 0;
        return ;
    }
    for (int i=1;i<=son[now][0];i++)
        if (son[now][i]!=fa){
            if (L==-1) L = son[now][i];
            else R = son[now][i];
            calc(son[now][i],now);
        }
    if (L==-1){
        f[now][0] =f[now][1] =  0;
        f[now][2] = 1;
    }else if (R==-1){
        //one
        f[now][0] = f[L][0];
        f[now][1] = f[L][1];
        f[now][2] = f[L][2];
    }else {
    		f[now][0] = f[L][0]+f[R][0];
    		f[now][1] = min(f[L][0]+f[R][1],f[L][0]+f[R][2]);
    		checkmin(f[now][1],min(f[R][0]+f[L][1],f[R][0]+f[L][2]));
    		f[now][2] = min(f[now][1],f[now][0])+1;
    		checkmin(f[now][2],f[L][2]+f[R][2]);


    }
}


int N,M;    
int main(){
#ifdef cwj
    freopen("in", "r", stdin);
#endif
    int i,j,a;
    while(scanf("%d%d",&N,&M)){
        if (N==0&&M==0) break;
        for (i=1;i<=N;i++){
            scanf("%d",&son[i][0]);
            for (j=1;j<=son[i][0];j++)
                scanf("%d",&son[i][j]);
            trup[i] = 0;
        }
        
        for (i=0;i<M;i++)
            scanf("%d",&a),trup[a] = 1;

        calc(1,-1);
        printf("%d\n",f[1][2]);
    }


}