#include <bits/stdc++.h>
using namespace std;
const int MAXN = 200005;
const int inf = 1e9 + 7;
vector<int> adj[MAXN], tcl[MAXN];
int ca[MAXN], p[MAXN], sz[MAXN], lvl[MAXN];
bool ins[MAXN], vis[MAXN], city[MAXN];
int ans = inf;
int dfs(int x, int par){
ins[x] = 1;
int ssz = 1;
for (int nn : adj[x]){
if (nn == par || lvl[nn] != -1) continue;
ssz += dfs(nn, x);
}
return sz[x] = ssz;
}
int dfs2(int x, int par, int ssz){
for (int nn : adj[x]){
if (nn == par || lvl[nn] != -1) continue;
if (sz[nn] > ssz / 2) return dfs2(nn, x, ssz);
}
return x;
}
void dfs3(int x, int par){
p[x] = par;
for (int nn : adj[x]){
if (nn == par || lvl[nn] != -1) continue;
dfs3(nn, x);
}
}
int calc(int cent){
queue<int> q; vis[cent] = 1; q.push(cent);
int res = 0;
while (!q.empty()){
int cn = q.front(), cc = ca[cn]; q.pop();
if (!city[cc]){
city[cc] = 1; res++;
for (int nn : tcl[cc]){
if (!ins[nn]) return inf;
if (vis[nn]) continue;
vis[nn] = 1; q.push(nn);
}
}
int par = p[cn];
if (par != -1 && !vis[par]){
vis[par] = 1; q.push(par);
}
}
return res;
}
void dfs4(int x, int par){
ins[x] = 0; vis[x] = 0; city[ca[x]] = 0;
for (int nn : adj[x]){
if (nn == par || lvl[nn] != -1) continue;
dfs4(nn, x);
}
}
void decomp(int x, int clvl){
int ssz = dfs(x, -1), cent = dfs2(x, -1, ssz);
lvl[cent] = clvl;
dfs3(cent, -1);
ans = min(ans, calc(cent));
dfs4(cent, -1);
for (int nn : adj[cent]){
if (lvl[nn] != -1) continue;
decomp(nn, clvl + 1);
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int nums, cnum; cin >> nums >> cnum;
for (int i = 1; i < nums; i++){
int a, b; cin >> a >> b;
adj[a].push_back(b); adj[b].push_back(a);
}
for (int i = 1; i <= nums; i++){
int c; cin >> c;
ca[i] = c; tcl[c].push_back(i);
}
memset(lvl, -1, sizeof(lvl));
decomp(1, 0);
cout << ans - 1;
}
