#pragma GCC optimize(3,"Ofast","inline")
#pragma G++ optimize(3,"Ofast","inline")
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#define R register int
#define re(i,a,b) for(R i=a; i<=b; i++)
#define ms(i,a) memset(a,i,sizeof(a))
#define MAX(a,b) (((a)>(b)) ? (a):(b))
#define MIN(a,b) (((a)<(b)) ? (a):(b))
using namespace std;
typedef long long LL;
namespace IO {
#include <cctype>
template <typename T>
inline void read(T &x){
x=0;
char c=0;
T w=0;
while (!isdigit(c)) w|=c=='-',c=getchar();
while (isdigit(c)) x=x*10+(c^48),c=getchar();
if(w) x=-x;
}
template <typename T>
inline void write(T x) {
if(x<0) putchar('-'),x=-x;
if(x<10) putchar(x+'0');
else write(x/10),putchar(x%10+'0');
}
template <typename T>
inline void writeln(T x) {
write(x);
putchar('\n');
}
}
using IO::read;
using IO::write;
using IO::writeln;
const int N=2e5+5;
int n,k,clk,scc,ans;
int dfn[N],c[N],mn[N],rr[N],idfn[N],f[N],low[N],st[N],tp,sz[N],bel[N];
bool ins[N],ban[N];
vector<int> e[N],v[N];
inline void cmin(int &x,int y) {
y < x ? x= y : 0;
}
void dfs(int x) {
idfn[dfn[x]=++clk]=x;
for(int i=0,y; i<e[x].size(); i++)
if(!dfn[y=e[x][i]]) f[y]=x,dfs(y);
rr[x]=clk;
}
void tarjan(int x) {
dfn[x]=low[x]=++clk;
st[++tp]=x;
ins[x]=1;
for(int i=0,y; i<v[x].size(); i++)
if(!dfn[y=v[x][i]]) tarjan(y),cmin(low[x],low[y]);
else if(ins[y]) cmin(low[x],dfn[y]);
if(dfn[x]==low[x]) {
int y;
scc++;
do {
y=st[tp--];
ins[y]=0;
bel[y]=scc;
sz[scc]++;
} while(y!=x);
}
}
int main() {
read(n);
read(k);
ans=k;
for(int i=1; i<n; i++) {
int x,y;
read(x);
read(y);
e[x].push_back(y);
e[y].push_back(x);
}
dfs(1);
memset(mn,0x3f,sizeof(mn));
for(int i=1; i<=n; i++) {
scanf("%d",&c[i]);
cmin(mn[c[i]],dfn[i]);
}
for(int i=1; i<=n; i++)
if(dfn[i]>rr[idfn[mn[c[i]]]])
mn[c[i]]=0;
for(int i=1; i<=n; i++)
if(dfn[i]^mn[c[i]])
v[c[i]].push_back(c[f[i]]);
memset(dfn,0,sizeof(dfn));
clk=0;
for(int i=1; i<=k; i++)
if(!dfn[i]) tarjan(i);
for(int i=1; i<=k; i++)
for(int j=0; j<v[i].size(); j++)
if(bel[i]^bel[v[i][j]])
ban[bel[i]]=1;
for(int i=1; i<=scc; i++)
if(!ban[i]) ans=MIN(ans,sz[i]);
writeln(ans-1);
return 0;
}
