1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for (int i = (a); i <= (b); ++i)
#define REPD(i,a,b) for (int i = (a); i >= (b); --i)
#define FORI(i,n) REP(i,1,n)
#define FOR(i,n) REP(i,0,int(n)-1)
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define ll long long
#define SZ(x) int((x).size())
#define DBG(v) cerr << #v << " = " << (v) << endl;
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define fi first
#define se second

const int maxn = 500500;

struct segment {
	int left, right;
	segment(int x=0) {left=right=x;}
	segment(int x, int y) {left=x; right=y;}
};

int n,m;
vi g[maxn];
int c[maxn];
long long R;
segment result[maxn];

segment dfs(int u, int par) {
	if (u < m) {
		return result[u] = segment(c[u]);
	}
	vector<segment> child;
	set<pii> events;
	vi t;
	FOR(i,g[u].size()) {
		int v = g[u][i];
		if (v==par) continue;
		dfs(v,u);
		//printf("result(%d) = %d %d (%d)\n", v, result[v].left, result[v].right, result[v].ispoint);
		//printf("Teraz wynik to %lld = %lld + %lld\n", R, rtemp, R-rtemp);
		events.insert(mp(result[v].left, child.size()));
		if (result[v].left != result[v].right) events.insert(mp(result[v].right, child.size()));
		child.pb(result[v]);
	}
	/*
	printf("wierzcholek %d: ", u);
	FOR(i,child.size()) printf("[%d %d (%d)], ", child[i].left, child[i].right, child[i].ispoint);
	printf("\n");
	printf("Wynik do tej pory to %lld\n", R);
	*/
	int lastleft = -1, lastright = -1;
	while (!events.empty()) {
		// zewnetrzne elementy
		int lowpos = events.begin()->se, highpos = events.rbegin()->se;
		segment low = child[lowpos], high = child[highpos];
		// to juz ostatni
		if (events.size() == 1) {
			if (low.left == -1) {
				if (lastleft == -1) {
					low.left=low.right;
				} else {
					low.left = lastleft;
				}
			}
			if (low.right == -1) {
				if (lastright == -1) {
					low.right=low.left;
				} else {
					low.right = lastright;
				}
			}
			return result[u] = low;
		}
		// przedzial po lewej -- zostaw prawy koniec
		if (low.left!=low.right && low.left != -1 && low.right != -1) {
			events.erase(mp(low.left, lowpos));
			child[lowpos].left = -1;
			lastleft = low.left;
			continue;
		}
		// przedzial po prawej -- zostaw lewy koniec
		if (high.left!=high.right && high.left != -1 && high.right != -1) {
			events.erase(mp(high.right, highpos));
			child[highpos].right = -1;
			lastright = high.right;
			continue;
		}
		// lewy po lewej i prawy po prawej -- darmowy przedzial
		if (events.size() == 2 && low.right == -1 && high.left == -1) {
			segment ret = segment(low.left, high.right);
			return result[u] = ret;
		}
		// lewy koniec po lewej -- za darmo
		if (low.right == -1) {
			events.erase(mp(low.left, lowpos));
			lastleft = low.left;
			continue;
		}
		// prawy koniec po prawej -- za darmo
		if (high.left == -1) {
			events.erase(mp(high.right, highpos));
			lastright = high.right;
			continue;
		}
		// lewy koniec po prawej / prawy koniec po lewej / punkt -- usun
		// ostatni
		if (events.size() == 2) {
			segment ret(low.right, high.left);
			return result[u] = ret;
		}
		// nie ostatni
		events.erase(mp(low.right, lowpos));
		events.erase(mp(high.left, highpos));
		lastleft = low.right;
		lastright = high.left;
	}
}

int med(int a, int b, int c) {
	if (a>b) swap(a,b);
	if (a>c) swap(a,c);
	if (b>c) swap(b,c);
	return b;
}

void dfstest(int u, int par) {
	if (u < m) return;
	if (par == -1) {
		c[u] = result[u].left;
	} else {
		if (result[u].left == result[u].right) c[u] = result[u].left;
		else c[u] = med(result[u].left, result[u].right, c[par]);
	}
	FOR(i,g[u].size()) {
		int v = g[u][i];
		if (v==par) continue;
		dfstest(v,u);
	}
}

int main () {
	scanf("%d%d", &n, &m);
	FOR(i,n-1) {
		int a,b;
		scanf("%d%d", &a, &b);
		a--; b--;
		g[a].pb(b);
		g[b].pb(a);
	}
	/*
	FOR(i,n) {
		printf("%d: ", i);
		FOR(j,g[i].size()) printf("%d ", g[i][j]);
		printf("\n");
	}
	*/
	FOR(i,m) scanf("%d", &c[i]);
	dfs(m,-1);
	//printf("result(%d) = %d %d (%d)\n", m, result[m].left, result[m].right, result[m].ispoint);
	dfstest(m,-1);
	R=0;
	FOR(i,n) FOR(j,g[i].size()) if (c[i] > c[g[i][j]]) R += c[i]-c[g[i][j]];
	printf("%lld\n", R);
	return 0;
}