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#include<bits/stdc++.h>
using namespace std;

vector<int> twe[509];
int ts[1009],tmp[1009];
int tpoj[509],tpar[509][509];


bool check(vector<int> *a, vector<int> *b, int m)
{
    int wyn=0;
    if(a->size()+b->size()<m) return false;
    for(vector<int>::iterator it=a->begin();it!=a->end();++it)
    {
        while(wyn>=0 && *it!=ts[wyn+1]) wyn=tmp[wyn];
        ++wyn;
        if(wyn==m) return true;
    }
    for(vector<int>::iterator it=b->begin();it!=b->end();++it)
    {
        while(wyn>=0 && *it!=ts[wyn+1]) wyn=tmp[wyn];
        ++wyn;
        if(wyn==m) return true;
    }
    return false;
}

long long int poteguj(int a, int b, int m)
{
    vector<int> va[2],vb[2];
    long long int pom=0;
    int start,kon;
    va[0].push_back(a);
    vb[0].push_back(b);
    while(min(va[pom%2].size(),vb[pom%2].size())<m)
    {
        va[(pom+1)%2].clear();
        start=0;
        kon=0;
        if(va[pom%2].size()>m) start=m-va[pom%2].size();
        if(vb[pom%2].size()>m) kon=m-vb[pom%2].size();
        for(vector<int>::iterator it=va[pom%2].begin()+start;it!=va[pom%2].end();++it)
        {
            for(vector<int>::iterator it2=twe[*it].begin();it2!=twe[*it].end();++it2) va[(pom+1)%2].push_back(*it2);
        }
        vb[(pom+1)%2].clear();
        for(vector<int>::iterator it=vb[pom%2].begin();it!=vb[pom%2].end()-kon;++it)
        {
            for(vector<int>::iterator it2=twe[*it].begin();it2!=twe[*it].end();++it2) vb[(pom+1)%2].push_back(*it2);
        }
        if(va[pom%2].size()+vb[pom%2].size()>=m && check(va,vb,m)) return pom+1;
        ++pom;
    }
    return 1e18;
}




void gen_poj()
{
    int ak;
    list<int> lista;
    tpoj[1]=1;
    lista.push_back(1);
    while(!lista.empty())
    {
        ak=lista.front();
        lista.pop_front();
        for(vector<int>::iterator it=twe[ak].begin();it!=twe[ak].end();++it)
            if(!tpoj[*it])
            {
                tpoj[*it]=tpoj[ak]+1;
                lista.push_back(*it);
            }
    }
}

void  gen_pair(int n)
{
    int v;
    list<pair<int,int> > lista;
    pair<int,int> ak;
    bool tb[509][509];
    for(int i=1;i<=n;++i)
        if(tpoj[i]>0)
        {
            for(vector<int>::iterator it=twe[i].begin();it!=twe[i].end()-1;++it)
                if(tpar[*it][*(it+1)]==0 || tpar[*it][*(it+1)]>tpoj[i]+1)
                {
                    tpar[*it][*(it+1)]=tpoj[i]+1;
                    tb[*it][*(it+1)]=true;
                    lista.push_back(make_pair(*it,*(it+1)));
                }
        }
    while(!lista.empty())
    {
        ak=lista.front();
        lista.pop_front();
        if(tb[ak.first][ak.second])
        {
            tb[ak.first][ak.second]=false;
            v=tpar[ak.first][ak.second]+1;
            while(true)
            {
                ak=make_pair(*twe[ak.first].rbegin(),*twe[ak.second].begin());
                if(tpar[ak.first][ak.second]!=0 && tpar[ak.first][ak.second]<=v) break;
                tb[ak.first][ak.second]=false;
                tpar[ak.first][ak.second]=v;
                ++v;
            }
        }
    }
}



int main()
{
    int n,m,roz,p;
    long long int wyn=1e18;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;++i)
    {
        scanf("%d",&roz);
        for(int j=0;j<roz;++j)
        {
            scanf("%d",&p);
            twe[i].push_back(p);
        }
    }
    for(int i=1;i<=m;++i)
    {
        scanf("%d",&ts[i]);
    }
    gen_poj();
    if(m==1)
    {
        if(tpoj[ts[1]]) printf("%d",tpoj[ts[1]]); else printf("-1");
        return 0;
    }
    gen_pair(n);
    if(m==2)
    {
        if(tpar[ts[1]][ts[2]]) printf("%d",tpar[ts[1]][ts[2]]); else printf("-1");
        return 0;
    }


                /*printf("\n");
                for(int i=1;i<=n;++i) printf("%d ",tpoj[i]); printf("\n");
                for(int i=1;i<=n;++i)
                {
                    for(int j=1;j<=n;++j) printf("%d ",tpar[i][j]); printf("\n");
                }*/

    tmp[0]=-1;
    for(int i=1;i<=m;++i)
    {
        tmp[i]=tmp[i-1];
        while(tmp[i]>=0 && ts[i]!=ts[tmp[i]+1]) tmp[i]=tmp[tmp[i]];
        ++tmp[i];
    }
    for(int i=1;i<=n;++i)
    {
        if(tpoj[i])
            for(int j=1;j<=n;++j)
                if(tpar[i][j]) wyn=min(wyn,tpar[i][j]+poteguj(i,j,m));     //printf("%d %d %d\n",i,j,wyn);}

    }
    printf("%lld",wyn);
    return 0;
}