#pragma opitimize("O3")
#include<bits/stdc++.h>
#define mp make_pair
#define F first
#define S second
#define iter(a) a.begin(), a.end()
#define lsort(a) sort(iter(a))
#define printv(a, b) { \
for(auto pv : a) b << pv << " "; \
b << "\n"; \
}
#define eb emplace_back
using namespace std;
typedef long long ll;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
ostream& operator<<(ostream& o, pll p){
return o << '(' << p.F << ',' << p.S << ')';
}
void waassert(bool t){
if(!t){
cout << "OAO\n";
exit(0);
}
}
struct Info{
pii mn, mx, al, lb, alb;
};
Info pull(Info a, Info b){
Info c;
c.mn = min(a.mn, b.mn);
c.mx = max(a.mx, b.mx);
c.al = max({a.al, b.al, mp(a.mx.F - 2 * b.mn.F, b.mn.S)});
c.lb = max({a.lb, b.lb, mp(- 2 * a.mn.F + b.mx.F, a.mn.S)});
c.alb = max({a.alb, b.alb, mp(a.al.F + b.mx.F, a.al.S), mp(a.mx.F + b.lb.F, b.lb.S)});
return c;
}
ostream& operator<<(ostream& o, Info info){
return o << '(' << info.mn << ',' << info.mx << ',' << info.al << ',' << info.lb << ',' << info.alb << ')';
}
struct Node{
int l = -1, r = -1;
int tag = 0;
Info info;
Info rv(){
Info t = info;
t.mn.F += tag;
t.mx.F += tag;
t.al.F -= tag;
t.lb.F -= tag;
return t;
}
};
struct SegmentTree{
vector<Node> st;
int ts = 0;
int build(int l, int r){
int id = ts++;
st[id].info.mn.S = st[id].info.mx.S = l;
st[id].info.al.S = l;
st[id].info.lb.S = l;
st[id].info.alb.S = l;
if(l == r) return id;
int m = (l + r) / 2;
st[id].l = build(l, m);
st[id].r = build(m + 1, r);
return id;
}
void push(int id){
st[st[id].l].tag += st[id].tag;
st[st[id].r].tag += st[id].tag;
st[id].info = st[id].rv();
st[id].tag = 0;
}
void modify(int l, int r, int v, int L, int R, int id){
if(l == L && r == R){
st[id].tag += v;
return;
}
int M = (L + R) / 2;
if(r <= M) modify(l, r, v, L, M, st[id].l);
else if(l > M) modify(l, r, v, M + 1, R, st[id].r);
else{
modify(l, M, v, L, M, st[id].l);
modify(M + 1, r, v, M + 1, R, st[id].r);
}
st[id].info = pull(st[st[id].l].rv(), st[st[id].r].rv());
}
pii query(int l, int r, int L, int R, int id){
if(l == L && r == R) return st[id].rv().mx;
push(id);
int M = (L + R) / 2;
if(r <= M) return query(l, r, L, M, st[id].l);
else if(l > M) return query(l, r, M + 1, R, st[id].r);
else return max(query(l, M, L, M, st[id].l), query(M + 1, r, M + 1, R, st[id].r));
}
void print(int l, int r, int id){
cerr << "print " << l << " " << r << " " << id << " " << st[id].l << " " << st[id].r << " " << st[id].info << "\n";
if(l == r) return;
push(id);
int m = (l + r) / 2;
print(l, m, st[id].l);
print(m + 1, r, st[id].r);
}
};
struct DSU{
vector<int> dsu;
vector<int> rk, up;
int cnt;
void init(int n){
dsu.resize(n + 1);
rk.resize(n + 1, 1);
up.resize(n + 1);
cnt = n;
for(int i = 1; i <= n; i++) dsu[i] = up[i] = i;
}
int findDSU(int a){
if(dsu[a] != a) dsu[a] = findDSU(dsu[a]);
return dsu[a];
}
void unionDSU(int a, int b){
a = findDSU(a);
b = findDSU(b);
if(a == b) return;
int tmp = up[a];
if(rk[a] < rk[b]) swap(a, b);
else if(rk[a] == rk[b]) rk[a]++;
up[a] = tmp;
cnt--;
dsu[b] = a;
}
};
int n;
vector<vector<int>> g;
vector<int> s;
vector<vector<int>> anc;
vector<int> in, out;
vector<int> et(1);
DSU dsu;
int ts = 0;
SegmentTree st;
void dfs1(int now, int p){
anc[0][now] = p;
in[now] = ++ts;
et.eb(now);
for(int i : g[now]){
if(i == p) continue;
dfs1(i, now);
ts++;
et.eb(now);
}
out[now] = ts;
}
void buildLCA(){
for(int i = 1; i < 20; i++){
for(int j = 1; j <= n; j++){
anc[i][j] = anc[i - 1][anc[i - 1][j]];
}
}
}
bool isAnc(int a, int b){
return in[a] <= in[b] && out[a] >= out[b];
}
int getLCA(int a, int b){
if(isAnc(a, b)) return a;
for(int i = 19; i >= 0; i--){
if(!isAnc(anc[i][a], b)) a = anc[i][a];
}
return anc[0][a];
}
int unionPath(int a, int b){
int lca = getLCA(a, b);
a = dsu.up[dsu.findDSU(a)];
b = dsu.up[dsu.findDSU(b)];
//cerr << a << " " << b << "\n";
while(!isAnc(a, lca)){
//cerr << a << " " << b << "\n";
st.modify(in[a], out[a], -1, 1, 2 * n - 1, 0);
dsu.unionDSU(anc[0][a], a);
a = dsu.findDSU(a);
a = dsu.up[a];
}
while(!isAnc(b, lca)){
//cerr << a << " " << b << "\n";
st.modify(in[b], out[b], -1, 1, 2 * n - 1, 0);
dsu.unionDSU(anc[0][b], b);
b = dsu.findDSU(b);
b = dsu.up[b];
}
return dsu.up[dsu.findDSU(lca)];
}
int fv = -1, fd = -1;
void dfs2(int now, int p, int dpt){
if(dpt > fd) fv = now, fd = dpt;
//cerr << "dfs2 " << now << " " << p << " " << dpt << "\n";
for(int i : g[now]){
if(i == p) continue;
if(dsu.findDSU(now) != dsu.findDSU(i)) dfs2(i, now, dpt + 1);
else dfs2(i, now, dpt);
}
}
void owo(){
//cerr << "owo\n";
int mid = st.st[0].info.alb.S;
int t1 = et[st.query(1, mid, 1, 2 * n - 1, 0).S];
int t2 = et[st.query(mid, 2 * n - 1, 1, 2 * n - 1, 0).S];
//cerr << mid << " " << t1 << " " << t2 << "\n";
unionPath(t1, t2);
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int k;
cin >> n >> k;
g.resize(n + 1);
s.resize(n + 1);
anc.resize(20, vector<int>(n + 1));
in.resize(n + 1);
out.resize(n + 1);
dsu.init(n);
vector<vector<int>> city(k + 1);
st.st.resize(4 * n);
for(int i = 0; i < n - 1; i++){
int u, v;
cin >> u >> v;
g[u].eb(v);
g[v].eb(u);
}
for(int i = 1; i <= n; i++){
cin >> s[i];
city[s[i]].eb(i);
}
dfs1(1, 1);
//printv(et, cerr);
buildLCA();
st.build(1, 2 * n - 1);
for(int i = 1; i <= n; i++){
st.modify(in[i], out[i], 1, 1, 2 * n - 1, 0);
}
for(int i = 1; i <= k; i++){
int v = city[i].front();
for(int j = 1; j < city[i].size(); j++){
v = unionPath(v, city[i][j]);
}
}
/*for(int i = 1; i < 2 * n; i++){
cerr << i << " " << st.query(i, i, 1, 2 * n - 1, 0) << "\n";
}
st.print(1, 2 * n - 1, 0);*/
int ans = 0;
while(dsu.cnt > 1){
owo();
ans++;
}
cout << ans << "\n";
return 0;
}
