#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
using namespace std;
typedef long long ll;
int n, m, dp[1010][1010];
string str;
vector<int> way;
void to_vector(string t)
{
	way.clear();
	int now = 0;
	t += " ";
	for(auto it : t)
	{
		if(it == ' ')
		{
			way.push_back(now);
			now = 0;
		}
		else now = now * 10 + it - 48;
	}
	return;
}
void Floyd()
{
	for(int k = 1; k <= n; k ++)
	{
		for(int i = 1; i <= n; i ++)
		{
			for(int j = 1; j <= n; j ++)
			{
				if(i != j && i != k && j != k) dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
			}
		}
	}
	return;
}
int main()
{
	IOS;
	memset(dp, 0x3f, sizeof dp);
	scanf("%d %d\n", &m, &n);
	while(m --)
	{
		getline(cin, str);
		to_vector(str);
		for(int j = 1; j <= way.size(); j ++)
		{
			dp[j][j] = 0;
			for(int k = j; k < way.size(); k ++) dp[way[j - 1]][way[k]] = 1;
		}
	}
	Floyd();
	if(dp[1][n] >= 0x3f3f3f3f) cout << "NO\n";
	else cout << dp[1][n] - 1 << endl;
	return 0;
}