#include<bits/stdc++.h>
using namespace std;
const int INF = 1e9;
int n,k,rez=INF;
vector<int> con[200005];
int color[200005];
int fr[200005];
int siz[200005];
bool iss[200005];
bool hascol[200005];
bool bagat[200005];
vector<int> ofcol[200005];
vector<int> active;
int parent[200005];
void get_sizes(int nod, int par)
{
if(ofcol[color[nod]].empty()) active.push_back(color[nod]);
ofcol[color[nod]].push_back(nod);
siz[nod]=1;
bagat[color[nod]]=0;
hascol[nod]=0;
for(auto adj:con[nod])
{
if(adj!=par && !iss[adj])
{
get_sizes(adj,nod);
siz[nod]+=siz[adj];
}
}
}
int get_centroid(int nod, int par, int tot)
{
for(auto adj:con[nod])
if(adj!=par && !iss[adj] && 2*siz[adj]>tot)
return get_centroid(adj,nod,tot);
return nod;
}
void dfs_parent(int nod)
{
for(auto adj:con[nod])
{
if(!iss[adj] && adj!=parent[nod])
{
parent[adj]=nod;
dfs_parent(adj);
}
}
}
int cate;
void baga_color(int col);
void baga_nod(int nod)
{
if(hascol[nod])
return;
hascol[nod]=1;
baga_color(color[nod]);
if(parent[nod]!=-1 && !hascol[parent[nod]])
baga_nod(parent[nod]);
}
void baga_color(int col)
{
if(bagat[col])
return;
cate++;
if((int)ofcol[col].size() != fr[col])
cate=INF;
bagat[col]=1;
for(auto x:ofcol[col])
{
baga_nod(x);
}
}
void centroid_decomposition(int c)
{
get_sizes(c,-1);
c = get_centroid(c,-1,siz[c]);
if((int)ofcol[color[c]].size()==fr[color[c]])
{
parent[c]=-1;
dfs_parent(c);
cate=0;
baga_color(color[c]);
rez = min(rez, cate-1);
}
for(auto x:active)
ofcol[x].clear();
active.clear();
iss[c]=1;
for(auto adj:con[c])
if(!iss[adj])
centroid_decomposition(adj);
}
signed main()
{
cin>>n>>k;
int a,b;
for(int i=1;i<n;i++)
{
cin>>a>>b;
con[a].push_back(b);
con[b].push_back(a);
}
for(int i=1;i<=n;i++)
{
cin>>color[i];
fr[color[i]]++;
}
centroid_decomposition(1);
cout<<rez;
return 0;
}
