#include <bits/stdc++.h>
using namespace std;
void setup()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int n, k, a, b, res = 1e9;
int c[200000], sz[200000], num[200000], pre[200000];
bool check[200000], vis[200000];
vector<int> g[200000], v[200000];
inline void PreCal(int node, int par)
{
sz[node] = 1;
vis[c[node]] = num[c[node]] = 0;
pre[node] = par;
for (auto &i : g[node])
{
if (i != par && !check[i])
{
PreCal(i, node);
sz[node] += sz[i];
}
}
}
inline int Centroid(int node, int par, int lim)
{
for (auto &i : g[node])
{
if (i != par && !check[i] && sz[i] * 2 > lim)
{
return Centroid(i, node, lim);
}
}
return node;
}
inline void Get(int node, int par)
{
num[c[node]]++;
for (auto &i : g[node])
{
if (i != par && !check[i])
{
Get(i, node);
}
}
}
inline void DFS(int node)
{
int val = 0, temp;
vector<int> cur;
PreCal(node, node);
Get(node, node);
node = Centroid(node, node, sz[node]); // From now, the centroid is the variable node
check[node] = true;
cur.push_back(c[node]);
while (!cur.empty())
{
temp = cur.back();
cur.pop_back();
if (vis[temp])
{
continue;
}
if (num[temp] != v[temp].size())
{
val = 1e9;
break;
}
val++;
vis[temp] = true;
for (auto &i : v[temp])
{
if (!vis[c[pre[i]]])
{
cur.push_back(c[pre[i]]);
}
}
}
res = min(res, val - 1);
for (auto &i : g[node])
{
if (!check[i])
{
DFS(i);
}
}
}
int main()
{
setup();
cin >> n >> k;
for (int i = 0; i < n - 1; ++i)
{
cin >> a >> b;
g[a - 1].push_back(b - 1);
g[b - 1].push_back(a - 1);
}
for (int i = 0; i < n; ++i)
{
cin >> c[i];
c[i]--;
v[c[i]].push_back(i);
}
DFS(0);
cout << res;
return 0;
}
