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#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

const long long INF = 1000LL*1000*1000*1000*1000*1000;
const int MAXN=500005, MAXM=500005;

struct NodeResult {
	long long cost;
	int begin, end;
	
	NodeResult() : cost(0), begin(0), end(0) {}
	NodeResult(long long cost, int begin, int end) : cost(cost), begin(begin), end(end) {}
};

struct IntervalEnd {
	int x;
	int id;
};

bool operator<(const IntervalEnd& lhs, const IntervalEnd& rhs) {
	if (lhs.x < rhs.x)
		return true;
	else if (lhs.x > rhs.x)
		return false;
	
	return lhs.id < rhs.id;
}

int N, M;

vector<int> edges[MAXN];
int edgesLeft[MAXN]={};

NodeResult nodeRes[MAXN];

bool done[MAXN]={};
bool inQueue[MAXN]={};

vector<int> processingQueue;

vector<IntervalEnd> ends;
int intervalCount[MAXN]={};

NodeResult processIntervals() {
	sort(ends.begin(), ends.end());
	
	//First phase (going right to left, finding cost of left-most):
	long long curCost=0, lastX=ends.rbegin()->x, curX;
	int passed=0;
	
	for (vector<IntervalEnd>::reverse_iterator rvit=ends.rbegin(); rvit!=ends.rend(); ++rvit) {
		curX = rvit->x;
		curCost += passed * (lastX-curX);
		lastX = curX;
		
		--intervalCount[rvit->id];
		if (intervalCount[rvit->id]==2)
			++passed;
	}
	
	//Second phase (going left to right, finding optimal cost):
	NodeResult res(INF, -1, -1);
	
	lastX = ends.begin()->x;
	int coming = ends.size()/2;
	int open=0;
	int closed=0;
	int curCostLeftMostX = ends.begin()->x;
	long long newCost;
	
	for (vector<IntervalEnd>::iterator vit=ends.begin(); vit!=ends.end(); ++vit) {
		curX = vit->x;
		newCost = curCost + closed * (curX-lastX) - coming * (curX-lastX);
		
		if (newCost != curCost) {
			curCost = newCost;
			curCostLeftMostX = curX;
		}
		
		if (res.cost > curCost || (res.cost == curCost && res.end-res.begin < curX - curCostLeftMostX)) {
			res.cost = curCost;
			res.begin = curCostLeftMostX;
			res.end = curX;
		}
		
		--intervalCount[vit->id];
		if (intervalCount[vit->id]==1) {
			--coming;
			++open;
		} else if (intervalCount[vit->id]==0) {
			--open;
			++closed;
		}
		
		lastX = curX;
	}
	
	return res;
}

void addToQueue(int node) {
	if (inQueue[node])
		return;
	
	processingQueue.push_back(node);
	inQueue[node]=true;
}

void processTree() {
	long long subtreeCost = 0;
	
	for (int i=1; i<=M; ++i)
		addToQueue(i);
	
	for (int i=0; i<(int)processingQueue.size(); ++i) {
		subtreeCost = 0;
		ends.clear();
		
		int node = processingQueue[i];
		done[node]=true;
		
		for (vector<int>::iterator vit=edges[node].begin(); vit!=edges[node].end(); ++vit) {
			if (done[*vit]) {
				//Gather data for processing:
				subtreeCost += nodeRes[*vit].cost;
				
				
				IntervalEnd e1, e2;
				
				int intervalId = ends.size()/2;
				intervalCount[intervalId] = 4;
				
				e1.id = e2.id = intervalId;
				
				e1.x = nodeRes[*vit].begin;
				e2.x = nodeRes[*vit].end;
				
				ends.push_back(e1);
				ends.push_back(e2);
				
				continue;
			} else {
				--edgesLeft[node];
				--edgesLeft[*vit];
				
				if (edgesLeft[*vit] <= 1)
					addToQueue(*vit);
			}
		}
		
		if (ends.size()!=0) {	//Not leafs
			nodeRes[node] = processIntervals();
			nodeRes[node].cost += subtreeCost;
		}
	}
}

int main() {
	scanf("%d %d", &N, &M);
	
	int a, b;
	for (int i=1; i<=N-1; ++i) {
		scanf("%d %d", &a, &b);
		edges[a].push_back(b);
		edges[b].push_back(a);
		++edgesLeft[a];
		++edgesLeft[b];
	}
	
	int point;
	for (int i=1; i<=M; ++i) {
		scanf("%d", &point);
		nodeRes[i].cost=0;
		nodeRes[i].begin=point;
		nodeRes[i].end=point;
	}
	
	//Special case:
	if (N==M) {	//Only leafs => N=M=2
		printf("%d\n", abs(nodeRes[1].begin-nodeRes[2].begin));
		return 0;
	}
	
	processTree();
	
	int root = *processingQueue.rbegin();
	printf("%lld\n", nodeRes[root].cost);
	
	return 0;
}