#pragma GCC optimize("Ofast" , "unroll-loops")
#include<bits/stdc++.h>
#define bit(i , j) ((j >> i) & 1)
#define fi first
#define se second
#define all(x) (x).begin() , (x).end()
using namespace std;
const int MAXN = 2e5+100;
const long long inf = 1e9+7;
#define int long long
#define pll pair<int , int>
#define MP make_pair
bitset<50010> g[MAXN];
vector<vector<int>> C[11];
int32_t main(){
//freopen("seq.inp", "r", stdin);
//freopen("seq.out", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n , k; cin >> n >> k;
for(int i = 0 ; i < n ; i++){
int D; cin >> D;
while(D--){
int x; cin >> x; g[min(i , x)][max(i , x)] = 1;
}
C[1].push_back({i});
}
bitset<50010> B;
int jj = 1;
while(C[jj].size() > 0){
for(auto x : C[jj]){
int lst = -1;
for(auto y : x){
if(lst == -1) B = g[y];
else B = B & g[y];
lst = y;
}
for(int j = B._Find_first() ; j < n ; j = B._Find_next(j)){
vector<int> tmp = x;
tmp.push_back(j);
C[jj+1].push_back(tmp);
}
}
jj++;
}
cout << jj-1 << "\n";
return 0;
}
