#include<bits/stdc++.h>
#define int long long
#define ll long long
#define down cout<<'\n';
#define debug cout<<" cucuucucuuu",down
#define NHP ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
#define modwwe int t;cin>>t; while(t--)
#define bit(i,j) (i>>j&1)
#define sobit(a) __builtin_popcountll(a)
#define task2 "ftree"
#define task "test"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define pb push_back
#define mask(k) (1<<k)
#define mp make_pair
#define checktime cerr << (double)clock() / CLOCKS_PER_SEC * 1000 << " ms";
using namespace std;
#define getchar_unlocked getchar
inline int scan()
{
char c = getchar_unlocked();
int x = 0;
while (c < '0' || c > '9')
{
c = getchar_unlocked();
}
while (c >= '0' && c <= '9')
{
x = (x << 1) + (x << 3) + c - '0';
c = getchar_unlocked();
}
return x;
}
void phongbeo();
const int inf = 1e14;
const ll mod2 = 1e9+7;
const int mod1 = 998244353;
const ll base=67;
int add(int x,int y)
{
if(x+y>=mod2) x-=mod2;
if(x+y<0)x+=mod2;
return x+y;
}
struct icd
{
long double a;
int b;
};
struct ib
{
int a;
int b;
};
struct ic
{
int a, b, c;
};
struct id
{
int a, b, c, d;
};
struct ie
{
int a, b, c, d, e;
};
int n, m, s1, s2, s4, s3, sf, k, s5, s6, mx, s7, s8, s9, mx2, res, dem2 = 0, dem = 0, s33, dem3, dem4, mid, l2, r2, center;
int i, s10, s12,k1,k2,k3,s11,lim,w,l,r,ans ;
int kk;
int el = 19;
main()
{
if(fopen(task2".inp","r"))
{
fin(task2);
fou(task2);
}
if(fopen(task".inp","r"))
{
fin(task);
fou(task);
}
NHP
/// cin>>s1;
//modwwe
phongbeo(),down
// checktime
}
int color[200001],st[18][200001],in[200001],depth[200001],ou[200001],low[200001],num[200001];
vector<int> v[4000001],ke[200001],lc[200001];
int id[18][200001];
bool cek[4000001],vis[200001];
void noi(int x,int y)
{
int par=color[x];
for(int i=0; i<18; i++)
if(bit(y,i))
{
v[par].pb(id[i][x]);
x=st[i][x];
}
}
bool check(int x,int y)
{
if(in[x]<=in[y]&&in[y]<=ou[x]) return 1;
return 0;
}
int lca(int x,int y)
{
if(check(x,y)) return x;
for(int i=17; i>=0; --i)
if(!check(st[i][x],y))
x=st[i][x];
return st[0][x];
}
void dfs(int x,int y)
{
in[x]=++dem;
st[0][x]=y;
depth[x]=depth[y]+1;
for(auto f:ke[x])
if(f^y)
dfs(f,x);
ou[x]=dem;
}
stack<int> s;
void dfs2(int x)
{
num[x]=low[x]=++dem;
s.push(x);
for(auto f:v[x])
{
if(num[f]==0) dfs2(f);
if(low[f]==inf)cek[x]=1;
low[x]=min(low[x],low[f]);
}
if(low[x]==num[x])
{
s2=-1;
s3=0;
bool de=0;
while(s2!=x)
{
s2=s.top();
s.pop();
low[s2]=inf;
if(s2<=k])
s3++;
if(cek[s2])de=1;
}
if(s3!=0)
if(!de)s4=min(s4,s3);
}
}
void phongbeo()
{
cin>>n>>k;
for(int i=1; i<n; i++)
cin>>l>>r,ke[l].pb(r),ke[r].pb(l);
for(int i=1; i<=n; i++)
cin>>color[i],id[0][i]=color[i],lc[color[i]].pb(i);
dfs(1,0);
ou[0]=n;
dem=k;
for(int i=1; i<18; i++)
for(int j=1; j<=n; j++)
{
id[i][j]=++dem;
v[id[i][j]].pb({id[i-1][j]});
v[id[i][j]].pb({id[i-1][st[i-1][j]]});
st[i][j]=st[i-1][st[i-1][j]];
}
for(int i=1; i<=k; i++)
{
int s=0;
for(auto x:lc[i])
{
if(s==0) s=x;
else s=lca(s,x);
}
for(auto x:lc[i])
noi(x,depth[x]-depth[s]+1);
}
s4=n+1;
dem=0;
for(int i=1; i<=k; i++)
if(!num[i])
dfs2(i);
cout<<s4-1;
}