//----------vahagng----------//
#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
using namespace std;
// using namespace __gnu_pbds;
// template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x <<" "; print(x); cerr << endl;
#else
#define dbg(x)
#endif
void print(long long t) { cerr << t; }
void print(int t) { cerr << t; }
void print(string t) { cerr << t; }
void print(char t) { cerr << t; }
void print(double t) { cerr << t; }
void print(long double t) { cerr << t; }
void print(unsigned long long t) { cerr << t; }
template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(T v[], V n) { cerr << "["; for (int i = 0; i < n; i++) { cerr << v[i] << " "; } cerr << "]"; }
template <class T, class V> void print(pair <T, V> p) { cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}"; }
template <class T> void print(vector <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(set <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(unordered_set <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T> void print(multiset <T> v) { cerr << "[ "; for (T i : v) { print(i); cerr << " "; } cerr << "]"; }
template <class T, class V> void print(map <T, V> v) { cerr << "[ "; for (auto i : v) { print(i); cerr << " "; } cerr << "]"; }
#define ll long long
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define ld long double
#define sz(v) v.size()
#define endl '\n'
const ll inf = 2e18, mod = 1e9 + 7, mod2 = 998244353;
void SetIO(string str = "") {
if (str != "") {
freopen((str + ".in").c_str(), "r", stdin);
freopen((str + ".out").c_str(), "w", stdout);
}
else {
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
}
}
void FastIO() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
}
const int N = 5e5 + 10, M = 2e7 + 10;
mt19937 rnd(chrono::system_clock::now().time_since_epoch().count());
ll binpow(ll a, ll b, ll m) {
ll res = 1;
while (b) {
if (b & 1) {
res = (res * a) % m;
}
b >>= 1;
a = (a * a) % m;
}
return res;
}
__int128_t gcd(__int128_t a, __int128_t b) {
while (b) {
a %= b;
swap(a, b);
}
return a;
}
__int128_t lcm(__int128_t a, __int128_t b) {
return a / gcd(a, b) * b;
}
ll n, k;
int adj[50005][50005], deg[N], st[N];
bool check(int b) {
for (int i = 1; i < b; i++) {
for (int j = i + 1; j < b; j++) {
if (!adj[st[i]][st[j]]) {
return 0;
}
}
}
return 1;
}
bool findC(int i, int l, int s) {
bool flag = 0;
for (int j = i + 1; j <= n - (s - l); j++) {
if (deg[j] >= s - 1) {
st[l] = j;
if (check(l + 1)) {
if (l < s) {
flag |= findC(j, l + 1, s);
}
else {
return 1;
}
}
}
}
return flag;
}
void solve(int tc) {
cin >> n >> k;
for (int i = 1; i <= n; i++) {
int d;
cin >> d;
while (d--) {
int k;
cin >> k;
k++;
adj[i][k] = 1;
adj[k][i] = 1;
deg[i]++;
}
}
int l = 1, r = k, ans = -1;
while (l <= r) {
int m = (l + r) / 2;
for (int i = 1; i <= n; i++) {
st[i] = 0;
}
if (findC(0, 1, m)) {
ans = m;
l = m + 1;
}
else {
r = m - 1;
}
}
cout << ans << endl;
}
void precalc() {
}
int main() {
// SetIO("teamwork");
FastIO();
int test_case = 1;
// cin >> test_case;
precalc();
int cnt = 1;
while (test_case--) {
solve(cnt++);
}
return 0;
}
