#include <bits/stdc++.h>
using namespace std;
int N, K, glob, sol = INT_MAX;
int A[200096], D[200096], COUNT[200096];
bool V[200096];
int SIZE[200096], PARENT[200096];
vector <int> VG[200096], I[200096];
inline void SDFS(int node, int parent = 0)
{
SIZE[node] = 1;
for(int x : VG[node])
{
if(V[x] || (x == parent)) continue;
SDFS(x, node);
SIZE[node] += SIZE[x];
}
return;
}
inline int CDFS(int node, int target, int parent = 0)
{
for(int x : VG[node])
{
if(V[x] || (SIZE[x] <= target) || (x == parent)) continue;
return CDFS(x, target, node);
}
return node;
}
inline void DFS(int node, int parent = 0)
{
if(D[A[node]] != glob)
{
I[A[node]] = vector <int>();
D[A[node]] = glob;
}
I[A[node]].push_back(node);
PARENT[node] = parent;
for(int x : VG[node])
{
if(V[x] || (x == parent)) continue;
DFS(x, node);
}
return;
}
inline void Centroid(int root)
{
SDFS(root);
int centroid = CDFS(root, SIZE[root] >> 1);
V[centroid] = true;
// cout << root << ' ' << centroid << '\n';
glob++;
DFS(centroid);
glob++;
queue <int> Q;
int node = centroid, temp = 0;
D[A[node]] = glob;
if(COUNT[A[node]] == I[A[node]].size()) for(int x : I[A[node]]) Q.push(x);
else temp = INT_MAX;
while(Q.size())
{
node = Q.front();
Q.pop();
if(!PARENT[node]) continue;
if(D[A[PARENT[node]]] != glob)
{
if(COUNT[A[PARENT[node]]] != I[A[PARENT[node]]].size()) {temp = INT_MAX; break;}
temp++;
D[A[PARENT[node]]] = glob;
for(int x : I[A[PARENT[node]]]) Q.push(x);
}
}
sol = min(temp, sol);
for(int x : VG[centroid]) if(!V[x]) Centroid(x);
return;
}
int main()
{
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cin >> N >> K;
int u, v;
for(int i = 2; i <= N; i++)
{
cin >> u >> v;
VG[u].push_back(v);
VG[v].push_back(u);
}
for(int i = 1; i <= N; i++)
{
cin >> A[i];
COUNT[A[i]]++;
}
Centroid(1);
cout << sol << '\n';
return 0;
}
