#include<iostream>
#include<set>
#include<vector>
#include<cassert>
#define MAXN 200005
using namespace std;
int N, K, best = 1<<30, C[MAXN];
vector <int> adj[MAXN], type[MAXN]; //adj and towns in each city
int cmp[MAXN], id = 1;
//Solve for a node
int par[MAXN];
bool done[MAXN];
vector <int> S;
set <int> Used;
void reroot(int u, int prev) {
if (cmp[u] != cmp[prev]) {return;}
par[u] = prev, done[u]=false;
for (auto v: adj[u]) {if (v != prev) {reroot(v, u);}}
}
int slv(int v) { //centre v
int ans = 0;
S.clear();
Used.clear();
reroot(v, v);
Used.insert(C[v]);
par[v] = 0;
for (auto k: type[C[v]]) {
if (cmp[k] != cmp[v]) {
return(1<<30);
} else {
S.push_back(k);
}
}
while (S.size()) {
int cur = S.back();
S.pop_back();
while (cur != 0 && !done[cur]) {
done[cur] = true;
if (Used.find(C[cur]) == Used.end()) {
for (auto k: type[C[cur]]) {
if (cmp[k] != cmp[cur]) {
return(1<<30);
} else {
S.push_back(k);
}
}
Used.insert(C[cur]);
}
cur = par[cur];
}
}
return(Used.size());
}
//Centroid decomp
int Size[MAXN];
int resize(int u, int prev) {
if (cmp[u] != cmp[prev]) {return(0);}
Size[u] = 1;
for (auto v: adj[u]) {
if (v != prev) {Size[u] += resize(v,u);}
}
//printf("Size[%d] = %d\n",u,Size[u]);
return(Size[u]);
}
int FindCentroid(int rt, int u, int prev) {
if (cmp[u] != cmp[prev]) {return(-1);}
int MaxSz = 0, SumSz=1;
for (auto v: adj[u]) {
if (v != prev && cmp[v] == cmp[u]) {
MaxSz = max(MaxSz, Size[v]);
SumSz += Size[v];
}
}
//printf("%d %d %d\n", Size[rt], MaxSz, SumSz);
if (2*MaxSz <= Size[rt]+1 && 2*SumSz + 1 >= Size[rt]) {
return(u);
}
for (auto v: adj[u]) {
if (v == prev) {continue;}
int res = FindCentroid(rt, v, u);
if (res > 0) {return(res);}
}
return(-1);
}
void relabel(int u, int prev, int cmp_prev) {
if (cmp[u] != cmp_prev) {return;}
cmp[u] = id;
for (auto v: adj[u]) {
if (v != prev) {relabel(v,u,cmp_prev);}
}
}
void decomp(int u) {
//printf("Decomp Node %d: cmp %d\n", u,cmp[u]);
resize(u, u);
int cent = Size[u] > 1 ? FindCentroid(u, u, u) : u;
//printf("Chosen Centroid: %d\n",cent);
assert(cent > 0);
best = min(best, slv(cent));
//cmp[cent] = -1;
for (auto v: adj[cent]) {
if (cmp[v] != cmp[cent]) {continue;}
relabel(v, cent, cmp[cent]);
id++;
decomp(v);
}
}
int main() {
//freopen("capin.txt","r",stdin);
scanf("%d %d", &N, &K);
for (int i=1; i<N; i++) {
int a,b;
scanf("%d %d",&a,&b);
adj[a].push_back(b);
adj[b].push_back(a);
}
for (int i=1; i<=N; i++) {
scanf("%d",&C[i]);
type[C[i]].push_back(i);
}
decomp(1);
printf("%d\n",best-1);
}
