#include<cstdio>

#include<iostream>

#include<cstring>

#define R register int

const int N=;

using namespace std;

inline int g() {

    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

    do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

}

int n,m,cnt;

int vr[N*N],nxt[N*N],w[N*N],fir[N],a[N],f[N][N];

inline void add(int u,int v,int ww) {vr[++cnt]=v,w[cnt]=ww,nxt[cnt]=fir[u],fir[u]=cnt;}

inline int dfs(int u) {

    if(u>n-m) {f[u][]=a[u]; return ;} R ret=;

    for(R i=fir[u];i;i=nxt[i]) { R v=vr[i],sz=dfs(v),ww=w[i];

        for(R j=ret;j>=;--j) for(R k=sz;k>=;--k)

            f[u][j+k]=max(f[u][j+k],f[u][j]+f[v][k]-ww); ret+=sz;

    } return ret;

}

signed main() {

    n=g(),m=g(); memset(f,0xbf,sizeof(f));

    for(R u=;u<=n-m;++u) { R sz=g();

        for(R j=,v,w;j<=sz;++j) v=g(),w=g(),add(u,v,w);

    } for(R i=n-m+;i<=n;++i) a[i]=g(); for(R i=;i<=n;++i) f[i][]=;

    dfs(); for(R i=m;i;--i) if(f[][i]>=) {printf("%d\n",i); break;}

}