#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define st first
#define nd second
#define FOR(__VAR, __START, __END) for(int __VAR=__START; __VAR<=__END; __VAR++)
#define FORB(__VAR, __START, __END) for(int __VAR=__START; __VAR>=__END; __VAR--)
#define FORK(__VAR, __START, __END, __DIFF) for(int __VAR=__START; __VAR<=END; __VAR+=__DIFF)
#define all(__VAR) (__VAR).begin(), (__VAR).end()
#define rall(__VAR) (__VAR).rbegin(), (__VAR).rend()
#define DEBUG(__VAR) cout << #__VAR << ": " << __VAR << endl;
template<typename __T1, typename __T2>
ostream & operator<<(ostream &out, pair<__T1, __T2> &__VAR)
{
cout << "[" << __VAR.st << ", " << __VAR.nd << "]";
return out;
}
template<typename __T>
ostream & operator<<(ostream &out, vector<__T> &__VAR)
{
cout << "[";
FOR(i, 0, (int)__VAR.size()-2)
cout << __VAR[i] << ", ";
if(__VAR.size()>0)
cout << __VAR[__VAR.size()-1];
cout << "]" << endl;
return out;
}
const int INF=1e9, LOG=20;
int n, k;
vector<int> color;
vector<int> colorLca;
vector<pii> preOrder;
vector<int> depth;
vector<vector<int>> tree, g;
vector<vector<int>> ancestor;
vector<vector<int>> colorInd;
vector<bool> vis;
void dfs1(int cur) {
static int nextInd=0;
preOrder[cur].st=preOrder[cur].nd=nextInd++;
colorInd[color[cur]].pb(preOrder[cur].st);
vis[cur]=true;
for(int v:tree[cur])
if(!vis[v]) {
ancestor[v][0]=cur;
depth[v]=depth[cur]+1;
dfs1(v);
preOrder[cur].nd=preOrder[v].nd;
}
}
int lca(int a, int b) {
if(depth[a]<depth[b])
swap(a,b);
int diff=depth[a]-depth[b];
for(int i=LOG-1; i>=0; i--)
if((1<<i)<=diff) {
diff-=1<<i;
a=ancestor[a][i];
}
if(a==b)
return a;
for(int i=LOG-1; i>=0; i--)
if(ancestor[a][i]!=ancestor[b][i]) {
a=ancestor[a][i];
b=ancestor[b][i];
}
return ancestor[a][0];
}
vector<int> comp;
stack<int> s;
vector<vector<int>> ig;
void dfs2(int cur) {
vis[cur]=true;
for(int v:g[cur])
if(!vis[v])
dfs2(v);
s.push(cur);
}
void dfs3(int ind, int cur) {
vis[cur]=true;
comp[cur]=ind;
for(int v:ig[cur])
if(!vis[v])
dfs3(ind, v);
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
tree.resize(n);
color.resize(n);
preOrder.resize(n);
colorLca.resize(k);
colorInd.resize(k);
g.resize(k);
vis.resize(n,0);
depth.resize(n,1);
ancestor.resize(n, vector<int>(LOG,0));
for(int i=0; i<n-1; i++) {
int a,b;
cin >> a >> b;
a--,b--;
tree[a].pb(b);
tree[b].pb(a);
}
for(int i=0; i<n; i++) {
cin >> color[i];
color[i]--;
}
dfs1(0);
for(int i=1; i<LOG; i++)
for(int v=0; v<n; v++)
ancestor[v][i]=ancestor[ancestor[v][i-1]][i-1];
for(int i=0; i<k; i++)
sort(colorInd[i].begin(), colorInd[i].end());
for(int i=0; i<n; i++)
colorLca[color[i]]=i;
for(int i=0; i<n; i++)
colorLca[color[i]]=lca(colorLca[color[i]], i);
for(int i=0; i<n; i++) {
int c=color[i];
if(depth[colorLca[c]]<depth[i])
g[c].pb(color[ancestor[i][0]]);
for(int v:tree[i])
if(preOrder[v].st>preOrder[i].st) {
auto it=lower_bound(colorInd[c].begin(), colorInd[c].end(), preOrder[v].st);
if(it!=colorInd[c].end() && (*it)<=preOrder[v].nd)
g[c].pb(color[v]);
}
}
comp.resize(k,0);
vis.resize(k);
fill(vis.begin(), vis.end(), false);
for(int i=0; i<k; i++)
if(!vis[i])
dfs2(i);
ig.resize(k);
for(int i=0; i<k; i++)
for(int j:g[i])
ig[j].pb(i);
int nextInd=0;
fill(vis.begin(), vis.end(), false);
while(!s.empty()) {
int cur=s.top();
s.pop();
if(vis[cur])
continue;
dfs3(nextInd++, cur);
}
vector<int> compSize(nextInd,0);
vector<bool> valid(nextInd,1);
for(int i=0; i<k; i++)
compSize[comp[i]]++;
for(int i=0; i<k; i++)
for(int j:g[i])
if(comp[i]!=comp[j])
valid[comp[i]]=0;
int result=INF;
for(int i=0; i<nextInd; i++)
if(valid[i])
result=min(result, compSize[i]);
cout << result-1 << '\n';
return 0;
}
