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import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Random;
import java.util.Stack;

import javax.management.RuntimeErrorException;

import static java.lang.Math.*;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.InputStreamReader;
public class roz {
	
	
	static class Seg{
		int left;int right;
		Seg(int a, int b) {
			left = a; right=b;
		}
		Seg(int x) {
			this(x,x);
		}
		
		long dist(int x) {
			if(x<left)return left -x;
			if(x>right)return x-right;
			return 0;
		}
		@Override
		public String toString() {
			return "["+left+", "+right+"]";
		}
	}
	
	static int[] searchEqBrut(Seg[]A) {
		int minVal = Integer.MAX_VALUE;
		int maxVal = Integer.MIN_VALUE;
		for(Seg x:A){
			minVal = min(minVal, x.left); maxVal = max(maxVal, x.right);
		}
		long bestSum = Long.MAX_VALUE;
		for(int x = minVal;x<=maxVal;x++) {
			long sum = dist(x,A);
			bestSum = min(sum,bestSum);
		}
		int[] res = new int[]{-1,-1};
		for(int x = minVal;x<=maxVal;x++) {
			long sum = dist(x,A);
			if(sum==bestSum) {
				if(res[0]==-1)res[0]=x;
				res[1]=x;
			}
		}
		return res;
	}
	
	static long dist(int x, Seg[]A) {
		long sum = 0;
		for(Seg y:A)sum+=y.dist(x);
		return sum;
	}
	
	static class ev implements Comparable<ev>{
		int p;
		boolean open;
		ev(int x, boolean b){
			p=x;open =b;
		}
		@Override
		public int compareTo(ev e) {
			if(p!=e.p) {
				return p-e.p;
			} else {
				if(open == e.open)return 0;
				return open?-1:1;
			}
		}
	}
	
	static int[] searchSmart(Seg[]A) {
		int[]res = new int[]{-1,-1};
		ev[]E = new ev[2*A.length];
		for(int i=0;i<A.length;i++) {
			E[2*i]= new ev(A[i].left, true);
			E[2*i+1]= new ev(A[i].right, false);
		}
		Arrays.sort(E);
		int onLeft =0;
		int onRight = A.length;
		for(ev e:E) {
			if(onLeft == onRight) res[1]=e.p;
			if(e.open) {
				onRight--;
			}
			else { 
				onLeft++;
			}
			if(onLeft==onRight)res[0]=e.p;
		}
		return res;
	}
	
	static Seg[] toSeg(int[]A) {
		Seg[]r = new Seg[A.length];
		for(int i=0;i<r.length;i++)r[i]=new Seg(A[i]);
		return r;
	}
	
	public static void test(){
		for(int t=0;;t++){
			Random R = new Random(t);
			int n = R.nextInt(200);
			Seg[]A = new Seg[n];
			for(int i=0;i<n;i++){
				int a = R.nextInt(2000);
				int b = R.nextInt(2000);
				A[i]=new Seg(min(a,b), max(a,b));
			}
			int[]r1 = searchEqBrut(A);
			int[]r2 = searchSmart(A);
			if(r1[0]!=r2[0] || r1[1]!=r2[1]){
				throw new RuntimeException("error "+t);
			} else {
				System.out.println("OK "+t);
			}
					
		}
	}
	
	static class Node {
		int idx;
		Seg seg = null;
		Node(int i){idx=i;}
		long cost =0;
		HashSet<Node>edges= new HashSet<>();
		ArrayList<Node>children= new ArrayList<>();
		@Override
		public boolean equals(Object obj) {
			return ((Node)obj).idx == idx;
		}
		
		void connectUp() {
			Node p = edges.iterator().next();
			p.children.add(this);
			// TODO: faster
			p.edges.remove(this);
		}
		Seg getSeg() {
			if(seg!=null)return seg;
			Seg[]A = new Seg[children.size()];
			// TODO: iter?
			for(int i=0;i<A.length;i++){
				A[i]=children.get(i).getSeg();
			}
			int[] bounds = searchSmart(A);
			seg = new Seg(bounds[0], bounds[1]);
			cost = dist(bounds[0], A);
			for(Node n:children)cost+=n.cost;
			return seg;
		}
		
		@Override
		public int hashCode() {
			return idx;
		}
	}
	
	static long doit(BufferedReader br) throws Exception{
		long stTime = System.currentTimeMillis();
		String[]s = br.readLine().split(" ");
		int n = Integer.parseInt(s[0]);int m = Integer.parseInt(s[1]);
		Node[]G = new Node[n+1];
		for(int i=1;i<=n;i++)G[i]= new Node(i);
		for(int i=0;i<n-1;i++) {
			s = br.readLine().split(" ");
			int a = Integer.parseInt(s[0]);int b = Integer.parseInt(s[1]);
			G[a].edges.add(G[b]);
			G[b].edges.add(G[a]);
		}
		for(int i=1;i<=m;i++){
			int x = Integer.parseInt(br.readLine());
			G[i].seg = new Seg(x,x);
		}
		if (n==2 && m==n) {
			return abs(G[1].seg.left - G[2].seg.left);
		}
		LinkedList<Node>toConnect = new LinkedList<>();
		for(int i=1;i<=m;i++) {
			toConnect.add(G[i]);
		}
		while(toConnect.isEmpty() ==false) {
			Node nn = toConnect.removeFirst();
			if(nn.edges.size()==0)continue;
			nn.connectUp();
			nn.getSeg();
			Node p = nn.edges.iterator().next();
			if(p.seg==null && p.edges.size()==1) {
				toConnect.add(p);
			}
		}
		Node root = null;
		for(int i=1;i<=n;i++) {
			if(G[i].edges.size()>1)throw new RuntimeException("Not connected");
			if(G[i].edges.size()==0){
				if(root ==null)root = G[i];
				else throw new RuntimeException("Two roots??");
			}
		}
		Seg finalSeg = root.getSeg();
		System.err.println(System.currentTimeMillis()-stTime);
		return root.cost;
	}
	
	public static void genLine() {
		System.out.println("500000 1");
		for(int i=1;i<500000;i++)System.out.println(i+" "+(i+1));
		System.out.println(42);
	}
	
	public static void genCater() {
		System.out.println("500000 499999");
		for(int i=1;i<500000;i++)System.out.println(i+" 500000");
		for(int i=1;i<500000;i++)System.out.println(i);
	}
	
	
	static void testKamil() throws Exception{
		for(int i=1;i<=60;i++) {
			String n = (i<10?"0":"")+i;
			BufferedReader br = new BufferedReader(new FileReader("kamil/roz"+n+".in"));
			BufferedReader brout = new BufferedReader(new FileReader("kamil/roz"+n+".out"));
			long resKam = Long.parseLong(brout.readLine());
			long res = doit(br);
			if(res==resKam)System.out.println("OK");
			else System.out.println("ERRRORR "+i);
		}
	}
public static void main(String[] args) throws Exception {
	//testKamil();
 
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			//new BufferedReader(new FileReader("cater.in"));
	System.out.println(doit(br));

	//genCater();
}
}