#include <bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;
typedef long long ll;
typedef pair<ll,ll>P;

class LCA{
public:
	vector<vector<int>>E;
	vector<vector<int>>par;
	vector<int>d1;
	int MAX_LOG=18;
	int n;
	LCA(){}
	LCA(int N){
		n=N;
		E=vector<vector<int>>(n);
		par=vector<vector<int>>(MAX_LOG,vector<int>(n));
		d1=vector<int>(n);
	}
	void add_edge(int a,int b){
		E[a].push_back(b);
		E[b].push_back(a);
	}
private:
	void dfs(int u,int p,int a){
		par[0][u]=p;d1[u]=a;
		for(auto&v:E[u]){
			if(v!=p)dfs(v,u,a+1);
		}
	}
	bool flag=false;
	void init(){
		dfs(0,-1,0);
		for(int i=1;i<MAX_LOG;i++)for(int j=0;j<n;j++){
			if(par[i-1][j]==-1)par[i][j]=-1;
			else par[i][j]=par[i-1][par[i-1][j]];
		}
		flag=true;
	}
public:
	int lca(int u,int v){
		if(!flag)init();
		if(d1[u]>d1[v])swap(u,v);
		for(int i=0;i<MAX_LOG;i++){
			if((d1[v]-d1[u])>>i&1)v=par[i][v];
		}
		if(u==v)return u;
		for(int i=MAX_LOG-1;i>=0;i--){
			if(par[i][u]!=par[i][v]){
				u=par[i][u];
				v=par[i][v];
			}
		}
		return par[0][u];
	}
};

template<class T>
class BIT{
public:
	vector<T>bit;
	T cnt;
	BIT(int n){
		bit=vector<T>(n+10);
		cnt=0;
	}
	void add(int k,T x){
		k++;
		while(k<(int)bit.size()){
			bit[k]+=x;
			k+=k&-k;
		}
		cnt+=x;
	}
	T sum(int k){
		k++;
		T res=0;
		while(k){
			res+=bit[k];
			k-=k&-k;
		}
		return res;
	}
	T sum2(int k){
		return cnt-sum(k);
	}
};

LCA lca;

int n,K;
int c[200000];
ll d[200000];

int L[200000],R[200000];//lca from left,right
int b[200000];

ll calc1(ll t){//score only
	ll ans=0;
	BIT<int>bit(K);
	vector<P>query;
	ll S=0;
	rep(i,K-2){
		int dep=lca.d1[lca.lca(L[i],c[K-1])];
		S+=d[i];
		query.push_back(P(t-dep-S,b[i]));
	}
	S=0;
	rep(i,K-1){
		S+=d[i];
		if(S+lca.d1[L[i]]<=t)ans++;
	}
	sort(query.begin(),query.end());
	vector<P>sum;
	ll s=0;
	for(int i=K-1;i>=0;i--){
		s+=d[i];
		sum.push_back(P(s,i));
	}
	sort(sum.begin(),sum.end());
	int g=0;
	for(auto p:query){
		while(g<sum.size()&&sum[g].first<=p.first){
			bit.add(sum[g].second,1);
			g++;
		}
		ans+=bit.sum2(p.second-1);
	}
	return ans;
}

struct st{
	ll a,b,c;
};

ll calc2(ll t){//score+depth
	ll ans=0;
	BIT<int>bit(K);
	vector<st>query;
	query.push_back({t,0,K});
	ll S=0;
	rep(i,K-2){
		S+=d[i];
		query.push_back({t-S,i+2,b[i]});
	}
	sort(query.begin(),query.end(),[](st a,st b){return a.a<b.a;});
	vector<P>sum;
	ll s=0;
	for(int i=K-1;i>=0;i--){
		s+=d[i];
		sum.push_back(P(s+lca.d1[R[i]],i));
	}
	sort(sum.begin(),sum.end());
	int g=0;
	for(auto p:query){
		while(g<sum.size()&&sum[g].first<=p.a){
			bit.add(sum[g].second,1);
			g++;
		}
		ans+=bit.sum(p.c-1)-bit.sum(p.b-1);
	}
	return ans;
}

ll C(ll t){
	ll cnt=0;
	cnt+=calc1(t);
	cnt+=calc2(t);
	return cnt;
}

int main(){
	cin>>n>>K;
	lca=LCA(n);
	rep(i,K){
		scanf("%d",&c[i]);c[i]--;
	}
	rep(i,K)scanf("%lld",&d[i]);
	rep(i,n-1){
		int a,b;scanf("%d%d",&a,&b);a--;b--;
		lca.add_edge(a,b);
	}
	lca.lca(0,1);
	for(int i=K-1;i>=0;i--){
		if(i==K-1)R[i]=c[i];
		else R[i]=lca.lca(R[i+1],c[i]);
	}
	rep(i,K){
		if(i==0)L[i]=c[i];
		else L[i]=lca.lca(L[i-1],c[i]);
	}
	rep(i,K-2){
		int ok=K-1,ng=i+1;
		int node=lca.lca(c[K-1],L[i]);
		while(ok-ng>1){
			int t=(ok+ng)/2;
			if(lca.lca(L[i],R[t])==node)ok=t;
			else ng=t;
		}
		b[i]=ok;
	}
	ll E=K*(ll)(K+1)/2+1;
	E=(E+1)/2-1;
	ll ok=2e14,ng=-2e14;
	while(ok-ng>1){
		ll t=(ok+ng)/2;
		if(C(t)>=E)ok=t;
		else ng=t;
	}
	cout<<ok<<endl;
}