#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0); cin.tie(0)
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
//#pragma GCC optimize("O3")
//#pragma GCC target("avx,avx2")
//#pragma GCC target("popcnt")
namespace{using namespace std;}
typedef long long ll;
typedef double db;
typedef long double ldb;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const ll MAX=1e5+10,P=1e9+7;
const ll INF=0x3f3f3f3f,oo=0x3f3f3f3f3f3f3f3f;
const ldb eps=1e-6;
int n,k;
vector<int> G[MAX];
int deg[MAX];
bool findc(int lim) {
queue<int> BFS;
for (int i=0;i<n;i++) {
if (deg[i]<lim-1) {
BFS.push(i);
// cout<<lim<<" "<<i<<" "<<deg[i]<<" i\n";
}
}
int cnt=0;
while (!BFS.empty()) {
cnt++;
int v=BFS.front();
BFS.pop();
for (int i:G[v]) {
if (deg[i]--==lim-1) BFS.push(i);
}
}
for (int i=0;i<n;i++) {
deg[i]=G[i].size();
// cout<<deg[i]<<" ";
}
// cout<<"\n";
// cout<<lim<<" "<<cnt<<"\n";
return (cnt!=n);
}
int main() {
speed;
cin>>n>>k;
for (int i=0;i<n;i++) {
int d;
cin>>d;
deg[i]=d;
while (d--) {
int x;
cin>>x;
G[i].push_back(x);
}
}
// for (int i=0;i<n;i++) cout<<deg[i]<<" ";
// cout<<"\n";
for (int i=2;i<=k;i++) {
if (!findc(i)) {
cout<<i-1<<"\n";
return 0;
}
}
cout<<k<<"\n";
return 0;
}
