//又抄解
#include <bits/stdc++.h>
using namespace std;
const int N = 510000;
int n, k, col[N], sz[N], parr[N], vis[N] = {0}, ans = INT_MAX, ins[N] = {0}, tt = 3, tt2 = 5;
bool block[N] = {0}, finish[N] = {0};
vector <int> e[N], bel[N];
int dfs_sz (int i, int par) {
sz[i] = 1;
parr[i] = par;
for (int j : e[i]) if (j != par and !block[j]) {
dfs_sz (j, i);
sz[i] += sz[j];
}
vis[i] = tt;
return sz[i];}
int dfs_cen (int i, int par, int tot) {
for (int j : e[i]) if (j != par and !block[j] and sz[j] * 2 > tot) return dfs_cen(j, i, tot);
return i;
}
void solve (int st) {
vector <int> color_used = {st};
queue<int> q;
tt2++;
ins[st] = tt2;
for (int j : bel[st]) {
q.push(j);
if (vis[j] != tt) return;
}
while (q.size()) {
int i = q.front(); q.pop();
if (ins[col[parr[i]]] != tt2) {
ins[col[parr[i]]] = tt2;
color_used.push_back(col[parr[i]]);
for (int x : bel[col[parr[i]]]) {
q.push(x);
if (vis[x] != tt) return;
}
}
}
ans = min(ans, (int)color_used.size() - 1);
}
void CD (int i) {
int tot = dfs_sz(i, i);
int cen = dfs_cen(i, i, tot);
dfs_sz(cen, cen);
solve(col[cen]);
block[cen] = 1;
tt++;
for (int j : e[cen]) if (!block[j]) CD(j);
}
int main () {
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n >> k;
for (int i = 1; i < n; i++) {
int x, y;
cin >> x >> y;
e[x].push_back(y);
e[y].push_back(x);
}
for (int i = 1; i <= n; i++) {
cin >> col[i];
bel[col[i]] . push_back(i);
}
CD(1);
cout << ans << '\n';
return 0;}
