/*
换车最少次数 = 坐车最少次数-1

1 2 3 4 5 6 7

每坐一次车cnt+1(那么从2→1 2→3 2→5 的权重都是1 代表坐一次车就可以到)
总共的边数最多 = C{2}{N}2 <= C{2}{500}2

所有权重都是1 可以用BFS来求最短距离
*/

#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<sstream>

using namespace std;
typedef pair<int,int> PII;
const int N=510,M=250000;
int m,n;
int h[N],e[M],ne[M],w[M],idx;
int dist[N];
int station[N];
bool st[N];

void add(int a,int b,int c)
{
    e[idx] = b;
    ne[idx] = h[a];
    w[idx] = c;
    h[a] = idx++;
}

int spfa()
{
    memset(dist,0x3f,sizeof dist);
    queue<int> q;
    q.push(1);
    st[1] = true;
    dist[1] = 0;
    while(q.size())
    {
        int ver = q.front();
        q.pop();
        st[ver] = false;
        for(int i=h[ver];i!=-1;i=ne[i])
        {
            int j = e[i];
            if(dist[j]>dist[ver]+w[i])
            {
                dist[j] = dist[ver]+w[i];
                if(!st[j])
                {
                    st[j]=true;
                    q.push(j);
                }
            }
        }
    }
    if(dist[n]==0x3f3f3f3f) return -1;
    return dist[n];
}

int dijkstra()
{
    memset(dist,0x3f,sizeof dist);
    priority_queue<PII,vector<PII>,greater<PII>> heap;
    heap.push({0,1});
    dist[1] = 0;
    while(heap.size())
    {
        int ver = heap.top().second;
        int d = heap.top().first;
        heap.pop();
        if(st[ver]) continue;
        st[ver] = true;
        for(int i=h[ver];i!=-1;i=ne[i])
        {
            int j = e[i];
            if(dist[j]>d+w[i])
            {
                dist[j] = d+w[i];
                heap.push({dist[j],j});
            }
        }
    }
    if(dist[n]==0x3f3f3f3f) return -1;
    return dist[n];
}
int main()
{
    memset(h,-1,sizeof h);//漏了初始化h了 导致死循环TLE
    cin >> m >> n;
    string line;
    getline(cin,line);
    while(m--)
    {
        getline(cin,line);
        stringstream ssin(line);
        int tot=0,p;
        while(ssin>>p) station[tot++]=p;
        for (int i = 0; i < tot; i ++ )//从前往后
            for (int j = i + 1; j < tot; j ++ )
                add(station[i],station[j],1);//加边加成add(i,j,1)了 查bug查了2h qwq
    }
    // int res = spfa();
    int res = dijkstra();
    if(res==-1) cout << "NO" << endl;
    else cout << res-1 << endl;
    // cout << dijkstra() << endl;
    return 0;
}