#include <bits/stdc++.h>
using namespace std;
struct Edge
{
    int v, w;
};
vector<Edge> e[3005];
int n, m;
int money[3005], mCnt;
int sz[3005];
int dp[3005][3005];
void dfs_dp(int now)
{
    sz[now] = 0;
    dp[now][0] = 0;
    for (int i = 0; i < e[now].size(); i++)
    {
        int v = e[now][i].v;
        int w = e[now][i].w;
        dfs_dp(v);
        //now 承载多少用户
        for (int j = sz[now]; j >= 0; j--)
            //v 承载多少用户
            for (int k = sz[v]; k >= 0; k--)
                dp[now][j + k] = min(dp[now][j + k], dp[now][j] + dp[v][k] + w);
        sz[now] += sz[v];
    }
    if (sz[now] == 0)
    {
        sz[now] = 1;
        dp[now][1] = -money[now];
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n - m; i++)
    {
        int k, v, w;
        cin >> k;
        while (k--)
        {
            cin >> v >> w;
            e[i].push_back((Edge){v, w});
        }
    }
    for (int i = n - m + 1; i <= n; i++)
        cin >> money[i];
    memset(dp, 0x3f, sizeof(dp));
    dfs_dp(1);
    for (int i = m; i >= 0; i--)
    {
        if (dp[1][i] <= 0)
        {
            cout << i << "\n";
            return 0;
        }
    }
    return 0;
}