#include <bits/stdc++.h>
using namespace std;

int n, m, d[50005], del[50005], ans = 1;
vector<int> G[50005], tmp; 
map<pair<int, int>, bool> M;
bool is[50005]; 

bool dfs(void){
    for (int i = 0; i < tmp.size(); i++)
        if (is[i] == 0) {
            is[i] = 1;
            for (int j = 0; j < i; j++)
                is[j] = 0; 
            return true;
        }
    return false;
}
void solve(void) {
    #define pii pair<int, int> 
    priority_queue<pii, vector<pii>, greater<pii>> q; 
    for (int i = 0; i < n; i++) q.emplace(0, i); 
    while (!q.empty()) {
        int now = q.top().second; q.pop(); 
        if (del[now]) continue; del[now] = 1; 
        tmp.clear(); 
        for (int u : G[now]) {
            if (!del[u]) tmp.push_back(u); 
            q.emplace(0, u); 
        }
        while (dfs()) {
            bool ok = 1; 
            vector<int> chs;
            for (int i = 0; i < tmp.size(); i++)
                if (is[i])
                    chs.push_back(tmp[i]);
            for (int i = 0; i < chs.size(); i++)
                for (int j = i + 1; j < chs.size(); j++)
                    if (!M[{chs[i], chs[j]}]) { ok = 0; goto ed; }
        ed:
            if (ok)
                ans = max(ans, (int)chs.size() + 1);
        }
        for (int i = 0; i < tmp.size(); ++i) is[i] = 0; 
    }
}
int main(void) {
    scanf("%d%d", &n, &m); 
    for (int i = 0; i < n; ++i) {
        int K; scanf("%d", &K);
        while (K--) {
            int x, y = i; scanf("%d", &x); 
            G[x].push_back(y); ++d[y]; M[{x, y}] = 1; 
        }
    }
    solve(); 
    return !printf("%d\n", ans); 
}