#include<cstdio>
#include<algorithm>
#include<vector>
#define N_ 210000
#define M_ 1010000
using namespace std;
vector<int>E[N_], G[M_], P[N_], H[M_];
int n, w[N_], K, C[N_], Dep[N_], par[N_][20], PPP[N_], Num[N_], Ed[N_], ReNum[N_], cnt;
void DFS(int a, int pp) {
par[a][0] = pp;
C[a] = 1;
for (int i = 0; i < 18; i++)par[a][i + 1] = par[par[a][i]][i];
for (auto &x : E[a]) {
if (x != pp) {
Dep[x] = Dep[a] + 1;
DFS(x, a);
C[a] += C[x];
}
}
}
void HLD(int a, int pp, int rt) {
Num[a] = ++cnt;
ReNum[cnt] = a;
G[n + cnt].push_back(w[a]);
PPP[a] = rt;
int Mx = -1, pv = -1;
for (auto &x : E[a]) {
if (x == pp)continue;
if (Mx < C[x])Mx = C[x], pv = x;
}
if (pv != -1) {
G[n+cnt + 1].push_back(n+cnt);
HLD(pv, a, rt);
}
for (auto &x : E[a]) {
if (x != pp && x != pv)HLD(x, a, x);
}
}
int LCA(int a, int b) {
if (Dep[a] < Dep[b])return LCA(b, a);
int d = Dep[a] - Dep[b], i;
for (i = 0; i < 18; i++)if ((d >> i) & 1)a = par[a][i];
for (i = 17; i >= 0; i--)if (par[a][i] != par[b][i])a = par[a][i], b = par[b][i];
if (a != b)a = par[a][0];
return a;
}
void MEdge(int st, int nd, int b, int e, int s, int l) {
if (s > l)return;
if (s <= b && e <= l) {
G[st].push_back(n + n + nd);
return;
}
int m = (b + e) >> 1;
if (s <= m)MEdge(st, nd * 2, b, m, s, l);
if (l > m)MEdge(st, nd * 2 + 1, m + 1, e, s, l);
}
void Make_Edge(int st, int a, int p) {
while (1) {
if (Dep[PPP[a]] <= Dep[p]) {
MEdge(st, 1, 1, n, Num[p], Num[a]);
return;
}
G[st].push_back(n+Num[a]);
a = par[PPP[a]][0];
}
}
void Build(int nd, int b, int e) {
if (b == e) {
G[n + n + nd].push_back(w[ReNum[b]]);
return;
}
int m = (b + e) >> 1;
G[n + n + nd].push_back(n + n + nd * 2);
G[n + n + nd].push_back(n + n + nd * 2 + 1);
Build(nd * 2, b, m);
Build(nd * 2 + 1, m + 1, e);
}
int ord[M_], SCC[M_], cc, sc, CC[M_];
bool chk[M_], vis[M_];
void DFS1(int a) {
vis[a] = 1;
for (auto &x : G[a]) {
if (!vis[x])DFS1(x);
}
ord[++cc] = a;
}
void DFS2(int a) {
SCC[a] = sc;
if (a <= K)CC[sc]++;
for (auto &x : H[a]) {
if (!SCC[x])DFS2(x);
}
}
int main() {
//freopen("input.txt", "r", stdin);
int i;
scanf("%d%d", &n,&K);
for (i = 1; i < n; i++) {
int a, b;
scanf("%d%d", &a, &b);
E[a].push_back(b);
E[b].push_back(a);
}
for (i = 1; i <= n; i++) {
scanf("%d", &w[i]);
P[w[i]].push_back(i);
}
DFS(1, 0);
HLD(1, 0, 1);
Build(1, 1, n);
for (i = 1; i <= K; i++) {
int a = P[i][0];
for (auto &t : P[i])a = LCA(a, t);
for (auto &t : P[i]) {
Make_Edge(i, t, a);
}
}
for (i = 1; i < M_; i++) {
for (auto &t : G[i]) {
H[t].push_back(i);
}
}
for (i = 1; i < M_; i++) {
if (!vis[i]) {
DFS1(i);
}
}
for (i = cc; i >= 1; i--) {
if (!SCC[ord[i]]) {
sc++;
DFS2(ord[i]);
}
}
for (i = 1; i < M_; i++) {
for (auto &t : G[i]) {
if (SCC[i] != SCC[t]) {
chk[SCC[i]] = 1;
}
}
}
int res = 1e9;
for (i = 1; i <= sc; i++) {
if (!chk[i] && CC[i])res = min(res, CC[i]);
}
printf("%d\n",res - 1);
}
