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#include "stdio.h"
#include "stdlib.h"

int M, N;

int E1[500100];
int E2[500100];
int CNT[500100];
int CNTK[500100];
int OFF[500100];
int NG[400200];
int toDo[500100];
long long COST[500100];
struct Range_t
{
	int a;
	int b;
};
Range_t RR[500100];

Range_t R[500100];
int rCnt;

int POINT[1000200];
int pointCnt;

int compr(const void *a, const void *b)
{
	return (*(int*)a - *(int*)b);
}

void clear()
{
	rCnt = 0;
	pointCnt = 0;
}

void addRange(Range_t *r)
{
	POINT[pointCnt] = r->a; pointCnt++;
	POINT[pointCnt] = r->b; pointCnt++;

	R[rCnt].a = r->a;
	R[rCnt].b = r->b;
	rCnt++;
}

void processRanges(int id, long long sumCost)
{
	// sort
	qsort(POINT, pointCnt, sizeof(int), compr);

	RR[id].a = POINT[pointCnt / 2 - 1];
	RR[id].b = POINT[pointCnt / 2];

	long long cost = sumCost;

	int x = RR[id].a;
	for (int i = 0; i < rCnt; i++)
	{
		if (x < R[i].a)
		{
			cost += (R[i].a - x);
		}
		else if (x > R[i].b)
		{
			cost += (x - R[i].b);
		}
	}

	COST[id] = cost;
}

int main()
{
	scanf("%i %i", &N, &M);

	for (int i = 0; i <= N; i++) { CNT[i] = 0; CNTK[i] = 0; }
	for (int i = 0; i < N - 1; i++)
	{
		scanf("%i %i", &E1[i], &E2[i]);
		CNT[E1[i]]++;
		CNT[E2[i]]++;
		if (E2[i] > M) {CNTK[E1[i]]++;}
		if (E1[i] > M) {CNTK[E2[i]]++;}
	}

	int offset = 0;
	for (int i = 0; i <= N; i++)
	{
		OFF[i] = offset;
		offset += CNT[i];
	}

	for (int i = 0; i <= N; i++) { CNT[i] = 0; }

	for (int i = 0; i < N - 1; i++)
	{
		NG[OFF[E1[i]] + CNT[E1[i]]] = E2[i];
		CNT[E1[i]]++;
		NG[OFF[E2[i]] + CNT[E2[i]]] = E1[i];
		CNT[E2[i]]++;
	}

	for (int i = 1; i <= M; i++)
	{
		int r;
		scanf("%i", &r);
		COST[i] = 0;
		RR[i].a = r; RR[i].b = r;
	}

	// GRAPH CONSTRUCTED
	int toDoCnt = 0;
	for (int i = M + 1; i <= N; i++)
	{
		RR[i].a = 0; RR[i].b = 0;

		if (CNTK[i] == 1 || CNTK[i] == 0)
		{
			toDo[toDoCnt] = i;
			toDoCnt++;
		}
	}

	while (toDoCnt > 0)
	{
		toDoCnt--;
		int id = toDo[toDoCnt];
	
		long long cost = 0;
		clear();
		for (int i = OFF[id]; i < OFF[id] + CNT[id]; i++)
		{
			int nid = NG[i];
			if (RR[nid].a == 0)
			{
				CNTK[nid]--;
				if (CNTK[nid] == 1)
				{
					toDo[toDoCnt] = nid;
					toDoCnt++;
				}
			}
			else
			{
				cost += COST[nid];
				// add range
				addRange(&RR[nid]);
			}
		}

		processRanges(id, cost);
	}

	printf("%i\n", COST[toDo[0]]);

	return 0;
}