C++ :

#include <cstdio>
struct Istream {
	template <class T> 
	Istream &operator >>(T &x) {
		static char ch;static bool neg;
		for(ch=neg=0;ch<'0' || '9'<ch;neg|=ch=='-',ch=getchar());
		for(x=0;'0'<=ch && ch<='9';(x*=10)+=ch-'0',ch=getchar());
		x=neg?-x:x;
		return *this;
	}
}is;
struct Ostream {
	template <class T>
	Ostream &operator <<(T x) {
		x<0 && (putchar('-'),x=-x);
		static char stack[233];static int top;
		for(top=0;x;stack[++top]=x%10+'0',x/=10);
		for(top==0 && (stack[top=1]='0');top;putchar(stack[top--]));
		return *this;
	}
	Ostream &operator <<(char ch) {
		putchar(ch);
		return *this;
	}
}os;
#include <set>
#include <vector>
#define int64 long long
const int MAXN=100000+11;
template <class T> inline
bool chkmx(T &a,T const &b) {
	return a<b?a=b,1:0;
}
std::vector<int> son[MAXN];
int lbr[MAXN],rbr[MAXN],brc,bra[MAXN<<1],longCh[MAXN];
void PreDFS(int pos) {
	bra[++brc]=0;
	lbr[pos]=brc;
	longCh[pos]=1;
	for(int &u:son[pos]) {
		PreDFS(u);
		chkmx(longCh[pos],longCh[u]+1);
	}
	bra[++brc]=1;
	rbr[pos]=brc;
}
int n,kDist;
std::vector<int> kSon[MAXN];
void GetKSon(int pos) {
	static int stack[MAXN],top;
	stack[++top]=pos;
	if(top>kDist+1) {
		kSon[stack[top-kDist-1]].push_back(pos);
	}
	for(int &u:son[pos]) {
		GetKSon(u);
	}
	top--;
}
typedef unsigned int64 Hash;
const Hash LBR=3,RBR=4,BASE=5;
Hash pHash[MAXN<<1],powBASE[MAXN<<1];
Hash SubStr(int l,int r) {
	return pHash[r]-pHash[l-1]*powBASE[r-l+1];
}
std::set<Hash> S;
bool Exist(int K) {
	kDist=K;
	for(int i=1;i<=n;++i) {
		kSon[i].clear();
	}
	S.clear();
	GetKSon(1);
	for(int pos=1;pos<=n;++pos) if(longCh[pos]>=kDist+1) {//kDist+1!!!!!!! !! !!
		int l=lbr[pos],r=rbr[pos];
		Hash hc=0;
		for(int &u:kSon[pos]) {
			r=lbr[u]-1;
			if(l<=r) {
				(hc*=powBASE[r-l+1])+=SubStr(l,r);
			}
			l=rbr[u]+1;
			r=rbr[pos];
		}
		if(l<=r) {
			(hc*=powBASE[r-l+1])+=SubStr(l,r);
		}
		if(!S.count(hc)) {
			S.insert(hc);
		} else {
			return 1;
		}
	}
	return 0;
}
int main() {
	is>>n;
	for(int i=1;i<=n;++i) {
		int cnt;is>>cnt;
		son[i].resize(cnt);
		for(int j=0;j<cnt;++j) {
			is>>son[i][j];
		}
	}
	PreDFS(1);
	powBASE[0]=1;
	for(int i=1;i<=brc;++i) {
		pHash[i]=pHash[i-1]*BASE+(bra[i]==0?LBR:RBR);
		powBASE[i]=powBASE[i-1]*BASE;
	}
	int L=0,R=n-1;
	while(L!=R) {
		int M=(L+R+1)>>1;
		if(Exist(M)) {
			L=M;
		} else {
			R=M-1;
		}
	}
	os<<L<<'\n';
	return 0;
}