#include <bits/stdc++.h>
using namespace std;
// #define int long long
#define sp << ' ' <<
#define nl << '\n'
const int MAXN = 2e5;
int n, k, color[MAXN], par[MAXN], s[MAXN], ans = MAXN;
vector<int> g[MAXN], h[MAXN];
bitset<MAXN> r, vis, bad;
void calcSize(int u){
s[u] = 1;
for(int v : g[u]) if(!s[v]) calcSize(v), s[u] += s[v];
}
int find(int u, int p, int sz){
bool f = 1;
while(f){
f = 0;
s[p] -= s[u], s[u] = sz;
for(int v : g[u]){
if(!r[v] && s[v] > sz/2){
p = u, u = v;
f = 1;
break;
}
}
}
return u;
}
void dfs(int u, int p, bool val){
par[u] = val ? p : -1;
if(val) vis[color[u]] = 0;
for(int v : g[u]) if(v != p && !r[v]) dfs(v, u, val);
}
void decompose(int c){
r[c = find(c, c, s[c])] = 1;
dfs(c, c, 1);
int res = 0;
vis[color[c]] = 1;
vector<int> st;
for(int i : h[color[c]]){
if(res == MAXN) break;
if(par[i] < 0) res = MAXN;
else st.push_back(i);
}
while(!st.empty() && res < MAXN){
int u = st.back(); st.pop_back();
if(!vis[color[par[u]]]){
if(bad[color[par[u]]]){
res = MAXN;
break;
}
++res;
for(int v : h[color[par[u]]]){
if(par[v] >= 0 && res < MAXN) st.push_back(v);
else res = MAXN;
}
if(res < MAXN) vis[color[par[u]]] = 1;
else bad[color[par[u]]] = 1;
}
}
ans = min(ans, res);
bad[color[c]] = 1;
dfs(c, c, 0);
for(int v : g[c]) if(!r[v]) decompose(v);
}
signed main(){
cin.tie(0)->sync_with_stdio(0);
int x, y; cin >> n >> k;
for(int i=1; i<n; ++i){
cin >> x >> y; --x, --y;
g[x].push_back(y);
g[y].push_back(x);
}
for(int i=0; i<n; ++i){
cin >> color[i]; --color[i];
h[color[i]].push_back(i);
}
calcSize(0);
decompose(0);
cout << ans;
}
