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#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<b;++i)
#define FORD(i,a,b) for(int i=a;i>=b;--i)
#define PB push_back
#define EB emplace_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vpii vector<pii>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
#define endl (char)10
#endif
using namespace std;
using ll = long long;
using ld = long double;

template <class T>
ostream& operator<< (ostream& os, const vector<T>& vec){
    for(auto& t : vec) os << t << " ";
    return os;
}
template<class T, class U>
ostream& operator<< (ostream& os, const pair<T, U>& p){
    os << p.FI << " " << p.SE;
    return os;
}
template<class T, class U>
istream& operator>> (istream& is, pair<T, U>& p){
    is >> p.FI >> p.SE;
    return is;
}
template <class T>
istream& operator>> (istream& is, vector<T>& vec){
    for(auto& p : vec) is >> p;
    return is;
}


int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    
    int n, z;
    cin >> n >> z;
    vvi V(n);
    V[0].assign(z, -1);
    vvi ile(n);
    ile[0].assign(z, 0);
    FOR(i,1,n){
		int k;
		cin >> k;
		V[i].resize(k);
		ile[i].assign(k, 0);
		FOR(j,0,k){
			int t;
			cin >> t;
			V[i][j] = t - 1;
		}
	}
    int ans = 0;
    FORD(t,n-1,0){
		int mile = 0;
		FOR(c,0,ile[t].size()){
			ile[t][c] = max(ile[t][c], 1);
			mile += ile[t][c];
			if (V[t][c] != -1) {
				ile[t - 1][V[t][c]] += ile[t][c];
			}
		}
		ans = max(ans, mile);
	}
	cout << ans << endl;
    
}