#include "bits/stdc++.h"
using namespace std;
using pii = pair <int, int>;
vector <int> v[200005];
vector <int> g[200005];
int c[200005];
int disc[200005], fin[200005], dep[200005];
int anc[20][200010];
const int logn = 19;
int cur;
bool del[200005];
int n, k;
int lca(int x, int y) {
if(dep[x] > dep[y]) {
swap(x, y);
}
for(int i = logn; i >= 0; i--) {
if(dep[y] - (1 << i) >= dep[x]) {
y = anc[i][y];
}
}
if(x == y) return x;
for(int i = logn; i >= 0; i--) {
if(anc[i][x] != anc[i][y]) {
x = anc[i][x];
y = anc[i][y];
}
}
return anc[0][x];
}
void dfs(int x, int par) {
anc[0][x] = par;
disc[x] = ++cur;
for(int i = 1; i <= logn; i++) {
anc[i][x] = anc[i - 1][anc[i - 1][x]];
}
for(auto i : g[x]) {
if(del[i]) continue;
if(i - par) {
dep[i] = 1 + dep[x];
dfs(i, x);
}
}
fin[x] = cur;
}
int par[200005];
int root(int x) {
if(par[x] == x) return x;
return par[x] = root(par[x]);
}
void join(int x, int y) {
x = root(x);
y = root(y);
if(x != y) {
par[x] = y;
}
}
bool done[200005];
int ans;
int solve(int col) {
queue <int> Q;
set <int> cont;
cont.insert(col);
Q.push(col);
while(!Q.empty()) {
int x = Q.front();
Q.pop();
vector <int> u = v[x];
sort(u.begin(), u.end(), [&] (int p, int q) { return disc[p] < disc[q]; });
for(int i = 1; i < v[x].size(); i++) {
u.push_back(lca(u[i - 1], u[i]));
}
sort(u.begin(), u.end(), [&] (int p, int q) { return disc[p] < disc[q]; });
stack <int> st;
int last = -1;
for(int i : u) {
if(i == last) continue;
while(!st.empty() && fin[st.top()] < disc[i]) {
st.pop();
}
if(!st.empty()) {
int cur = i;
while(dep[st.top()] < dep[cur]) {
if(done[c[cur]]) return k;
if(!cont.count(c[cur])) Q.push(c[cur]);
cont.insert(c[cur]);
join(cur, anc[0][cur]);
cur = root(anc[0][cur]);
}
}
else {
if(done[c[i]]) return k;
if(!cont.count(c[i])) Q.push(c[i]);
cont.insert(c[i]);
st.push(i);
}
last = i;
}
}
return cont.size() - 1;
}
int sub[200010], opt[200010];
void subtree(int x, int par) {
sub[x] = 1;
for(auto i : g[x]) {
if(del[i]) continue;
if(i - par) {
subtree(i, x);
sub[x] += sub[i];
}
}
}
int centroid(int x, int par, int range) {
for(auto i : g[x]) {
if(del[i]) continue;
if(i - par) {
if(sub[i] > range) return centroid(i, x, range);
}
}
return x;
}
void process(int x, int p, int root) {
if(opt[c[x]] == -1) {
opt[c[x]] = root;
} else if (opt[c[x]] != root) {
done[c[x]] = true;
}
for(auto i : g[x]) {
if(del[i]) continue;
if(i - p) {
process(i, x, root);
}
}
}
void reset(int x, int p) {
par[x] = x;
opt[c[x]] = -1;
for(auto i : g[x]) {
if(del[i]) continue;
if(i - p) {
reset(i, x);
}
}
}
void decomp(int x) {
subtree(x, 0);
x = centroid(x, 0, sub[x] / 2);
reset(x, 0);
del[x] = true;
if(!done[c[x]]) {
ans = min(ans, solve(c[x]));
done[c[x]] = true;
}
for(int i : g[x]) {
if(!del[i]) {
process(i, x, i);
}
}
for(auto i : g[x]) {
if(!del[i]) {
decomp(i);
}
}
}
int main(int argc, char const *argv[])
{
scanf("%d %d", &n, &k);
for(int i = 1; i < n; i++) {
int p, q;
scanf("%d %d", &p, &q);
g[p].emplace_back(q);
g[q].emplace_back(p);
}
for(int i = 1; i <= n; i++) {
scanf("%d", &c[i]);
v[c[i]].push_back(i);
}
dfs(1, 0);
ans = k;
decomp(1);
printf("%d\n", ans);
return 0;
}
