[BZOJ2502]清理雪道

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <stack>
#include <vector>
#include <queue>
#include <cstring>
#include <string>
#include <map>
#include <set>
using namespace std;

const int BufferSize = 1 << 16;
char buffer[BufferSize], *Head, *Tail;
inline char Getchar() {
	if(Head == Tail) {
		int l = fread(buffer, 1, BufferSize, stdin);
		Tail = (Head = buffer) + l;
	}
	return *Head++;
}
int read() {
	int x = 0, f = 1; char c = Getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = Getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = Getchar(); }
	return x * f;
}

#define maxn 110
#define maxm 40010
#define oo 2147483647
#define inf 100000
#define LL long long
struct Edge { int from, to, flow, cost; } ;
struct ZKW {
	int n, m, s, t, head[maxn], next[maxm];
	LL cost, ans;
	Edge es[maxm];
	bool inq[maxn];
	LL d[maxn];
	bool vis[maxn];
	void init(int nn) {
		n = nn; m = 0; memset(head, -1, sizeof(head));
		return ;
	}
	void AddEdge(int a, int b, int c, int d) {
		es[m] = (Edge){ a, b, c, d }; next[m] = head[a]; head[a] = m++;
		es[m] = (Edge){ b, a, 0, -d }; next[m] = head[b]; head[b] = m++;
		return ;
	}
	bool BFS() {
		memset(inq, 0, sizeof(inq));
		for(int i = 1; i <= n; i++) d[i] = oo;
		deque <int> Q;
		Q.push_front(t); inq[t] = 1; d[t] = 0;
		while(!Q.empty()) {
			int u = Q.front(); Q.pop_front(); inq[u] = 0;
			for(int i = head[u]; i != -1; i = next[i]) {
				Edge& e = es[i^1];
				if(e.flow && d[e.from] > d[u] + e.cost) {
					d[e.from] = d[u] + e.cost;
					if(!inq[e.from]) {
						inq[e.from] = 1;
						if(Q.empty() || d[e.from] <= d[Q.front()]) Q.push_front(e.from);
						else Q.push_back(e.from);
					}
				}
			}
		}
		if(d[s] == oo) return 0;
		for(int i = 0; i < m; i++) es[i].cost += d[es[i].to] - d[es[i].from];
		cost += d[s];
		return 1;
	}
	int DFS(int u, int a) {
		if(u == t || !a){ ans += cost * a; return a; }
		vis[u] = 1;
		int flow = 0, f;
		for(int i = head[u]; i != -1; i = next[i]) {
			Edge& e = es[i];
			if(!vis[e.to] && e.flow && !e.cost && (f = DFS(e.to, min(a, e.flow)))) {
				a -= f; flow += f;
				e.flow -= f; es[i^1].flow += f;
				if(!a) return flow;
			}
		}
		return flow;
	}
	int MaxFlow(int ss, int tt) {
		s = ss; t = tt;
		int flow = 0, tmp;
		while(BFS()) {
			if(cost >= 0) break;
			do {
				memset(vis, 0, sizeof(vis));
				tmp = DFS(s, oo);
				flow += tmp;
			} while(tmp);
		}
		return flow;
	}
} sol;

int in[maxn], out[maxn];
int main() {
	int n = read(), s = n + 1, t = s + 1;
	sol.init(n + 2);
	for(int i = 1; i <= n; i++) {
		int m = read();
		while(m--) {
			int a = read();
			in[a]++; out[i]++;
			sol.AddEdge(i, a, 1, -inf);
			sol.AddEdge(i, a, oo, 0);
		}
	}
	for(int i = 1; i <= n; i++) {
		if(!in[i]) sol.AddEdge(s, i, oo, 0);
		if(!out[i]) sol.AddEdge(i, t, oo, 0);
	}
	
	printf("%d\n", sol.MaxFlow(s, t));
	
	return 0;
}