#include <iostream>
#include <vector>
#include <stdio.h>
using namespace std;

int DP[3003][3003] = {0};

int get[3003];//从客户的所得

int N, M;

void print(){
	for(int i = 1; i <= N; i++){
		for(int j = 0; j <= M; j++){
			cout << "(" <<i << "," << j << "):" << DP[i][j] << " ";
		}
		cout << endl;
	}
}

struct node{
	int num;
	int sucGs;
	vector<int> suc;
	vector<int> costs;
	node(int n): num(n), sucGs(-1){}
	int getGS();
	void Dp();
};

node* nodes[3003] = {NULL};

int node::getGS(){
	if(sucGs != -1) return sucGs;
	if(num > N-M) {
		sucGs = 1;
		return 1;
	}
	int res = 0;
	int len = suc.size();
	for(int i = 0; i < len; i++){
		res += nodes[suc[i]]->getGS();
	}
	sucGs = res;
	return res;
}

void node::Dp(){
	//cout << "DPing:" << num << endl;
	//print();
	if(num > N-M) return;
	int len = suc.size();
	for(int i = 0; i < len; i++) nodes[suc[i]]->Dp();
	int row = len+1, column = sucGs + 1;
	int *dp = new int[row*column];
	int *gs = new int[row];
	gs[0] = 0;
	for(int i = 1; i < row; i++){
		gs[i] = gs[i-1] + nodes[suc[i-1]]->sucGs;
	}
	dp[0] = 0;
	for(int i = 1; i < len; i++){
		for(int j = 0; j <= gs[i]; j++) dp[i*column+j] = -2147483648;
		int cha = nodes[suc[i-1]]->sucGs;
		for(int j = 0; j <= gs[i-1]; j++){
			for(int k = 0; k <= cha; k++){
				int temp = dp[(i-1)*column+j] + DP[suc[i-1]][k] - (k==0? 0: costs[i-1]);
				if(temp > dp[i*column+j+k]) dp[i*column+j+k] = temp;
			}
		}
	}
	for(int j = 0; j <= sucGs; j++) DP[num][j] = -2147483648;
	int cha = nodes[suc[len-1]]->sucGs;
	for(int j = 0; j <= gs[len-1]; j++){
		for(int k = 0; k <= cha; k++){
			int temp = dp[(len-1)*column+j] + DP[suc[len-1]][k] - (k==0? 0 : costs[len-1]);
			if(temp > DP[num][j+k]) DP[num][j+k] = temp;
		}
	}
	delete [] dp;
	delete [] gs;
	//print();
}

int main() {
	node *root = new node(1);
	nodes[1] = root;
	//int N, M;
	scanf("%d%d", &N, &M);
	for(int i = 1; i <= N-M; i++){
		int gs;
		scanf("%d", &gs);
		node *temp;
		if(nodes[i] == NULL){
			temp = new node(i);
			nodes[i] = temp;
		}
		else{
			temp = nodes[i];
		}
		for(int j = 0; j < gs; j++){
			int suc, cost;
			scanf("%d%d", &suc, &cost);
			temp->suc.push_back(suc);
			temp->costs.push_back(cost);
		}
	}
	for(int i = N-M+1; i <= N; i++) {
		node *temp = new node(i);
		nodes[i] = temp;
		scanf("%d", &get[i]);
		DP[i][1] = get[i];
	}

	root->getGS();
	//for(int i = 1; i <= N; i++){cout << nodes[i]->sucGs << endl;}
	//cout << 1 << endl;
	root->Dp();
	for(int i = M; i >= 0; i--){
		if(DP[1][i] >= 0){
			printf("%d\n", i);
			break;
		}
	}
	return 0;
}