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#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i = (a); i <= (b); ++i)
#define FORD(i,a,b) for(int i = (a); i >= (b); --i)
#define RI(i,n) FOR(i,1,(n))
#define REP(i,n) FOR(i,0,(n)-1)
#define mini(a,b) a=min(a,b)
#define maxi(a,b) a=max(a,b)
#define mp make_pair
#define pb push_back
#define st first
#define nd second
#define sz(w) (int) w.size()
typedef vector<int> vi;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
const int inf = 1e9 + 5;
const int nax = 5e5 + 5;

vi w[nax];
int val[nax];
ll RESULT;

ll f(int x, const vector<pii> & L) {
	ll s = 0;
	for(const pii & p : L) {
		if(x <= p.st) s += p.st - x;
		else if(x >= p.nd) s += x - p.nd;
	}
	return s;
}

pii dfs(int a, int par = -1) {
	if(sz(w[a]) == 1) return mp(val[a], val[a]);
	vector<pii> L;
	for(int b : w[a]) if(b != par)
		L.pb(dfs(b, a));
	int low = 1, high = 500 * 1000;
	while(low < high) {
		int med = (low + high) / 2;
		if(f(med, L) > f(med+1, L)) low = med + 1;
		else high = med;
	}
	int start = low;
	ll MIN = f(start, L);
	high = 500 * 1000;
	while(low < high) {
		int med = (low + high + 1) / 2;
		if(f(med, L) == MIN) low = med;
		else high = med - 1;
	}
	RESULT += MIN;
	return mp(start, low);
}

int main() {
	int n, m;
	scanf("%d%d", &n, &m);
	REP(_, n - 1) {
		int a, b;
		scanf("%d%d", &a, &b);
		w[a].pb(b);
		w[b].pb(a);
	}
	RI(i, m) scanf("%d", &val[i]);
	if(n == 2) {
		printf("%d\n", abs(val[1] - val[2]));
		return 0;
	}
	int root = 1;
	while(sz(w[root]) == 1) ++root;
	dfs(root);
	printf("%lld\n", RESULT);
	return 0;
}