#include <bits/stdc++.h>
using namespace std;
int main() {
int n, useless;
cin >> n >> useless;
vector<vector<int>> adj(n + 1);
set<pair<int, int>> pr;
vector<pair<int, int>> vp;
for(int i = 1; i <= n; i++) {
int x;
cin >> x;
vp.push_back({x, i});
while(x--) {
int a;
cin >> a;
a++;
adj[i].push_back(a);
pr.insert({min(a, i), max(a, i)});
}
}
sort(vp.begin(), vp.end());
vector<vector<vector<int>>> v(n + 1);
for(int i = 1; i <= n; i++) {
v[i].push_back({i});
}
int ans = 0;
while(true) {
vector<vector<vector<int>>> curr(n + 1);
ans++;
bool ok = 0;
for(int ii = 1; ii <= n; ii++) {
int i = vp[ii - 1].second;
// cout << "la " << i << "\n";
for(auto it : adj[i]) {
// cout << "vecin " << it << ':';
vector<int> cp;
bool used = 0;
for(auto s : v[it]) {
bool nf = 0;
for(auto j : s) {
if(pr.find({min(i, j), max(i, j)}) == pr.end()) {
nf = 1;
break;
}
}
if(!nf) {
// cout << " merge, face: ";
cp = s;
used = 1;
ok = 1;
break;
}
}
if(used) {
cp.push_back(i);
curr[i].push_back(cp);
}
}
}
if(!ok) {
break;
}
swap(v, curr); // o(1) plsplspls
}
cout << ans;
return 0;
}
