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#include <bits/stdc++.h>

using namespace std;
const int MAXN = 500;
const int MAXM = 1000;
const int LIMIT = 9000000;

int n, m, a, b;
vector <int> R[MAXN + 5];
vector <int> pattern;
vector <int> seq;
int p[MAXM + 5];
int cnt;

bool is_pattern_present();
void knuth();
void replace();

int main() {
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= n; ++i) {
        scanf("%d", &a);
        for(int j = 0; j < a; ++j) {
            scanf("%d", &b);
            R[i].push_back(b);
        }
    } 
    for(int i = 0; i < m; ++i) {
        scanf("%d", &a);
        pattern.push_back(a);
    }
    knuth(); 
    cnt = 1;
    seq.push_back(1);
    while(!is_pattern_present()) {
       if(seq.size() > LIMIT) {
            printf("-1\n");
            return 0;
       } 
       ++cnt;
       replace();
    }
    printf("%d\n", cnt);
    return 0;
}

bool is_pattern_present() {
    int act = 0;
    for(int i = 0; i < seq.size(); ++i) {
        while(act > 0 && seq[i] != pattern[act]) act = p[act - 1];
        if(seq[i] == pattern[act]) ++act;
        if(act == pattern.size()) return true;
    }
    return false;
}

void replace() {
    vector <int> tmp;
    for(int i = 0; i < seq.size(); ++i) {
        for(int j = 0; j < R[seq[i]].size(); ++j) {
            tmp.push_back(R[seq[i]][j]);
        }
    }
    seq = tmp;
}

void knuth() {
    int act = 0;
    for(int i = 1; i < pattern.size(); ++i) {
        while(act > 0 && pattern[i] != pattern[act]) act = p[act - 1];
        if(pattern[i] == pattern[act]) ++act; 
        p[i] = act;
    }
}