#include<algorithm>

 #include<cstdio>

 #include<cmath>

 #include<cstring>

 #include<iostream>

 #include<time.h>

 #define inf 0x7fffffff

 struct edge{

     int u,v,id;

 }e[];

 int tot,go[],first[],next[];

 int Tot,Go[],First[],Next[];

 int c[],b[],son[],ans,vis[],pd;

 int pass[],op[],C[],Cnt,block,sum,B[];

 int id1,id2;

 int n,k;

 int read(){

     char ch=getchar();int t=,f=;

     while (ch<''||ch>''){if (ch=='-') f=-;ch=getchar();}

     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}

     return t*f;

 }

 void Dfs(int x,int fa){

     if (vis[x]) return;

     c[x]=b[x];son[x]=;

     for (int i=first[x];i;i=next[i]){

         int pur=go[i];

         if (pur==fa) continue;

         if (pass[i]) continue;

         Dfs(pur,x);

         son[x]+=son[pur];

         c[x]+=c[pur];

     }

     if (c[x]&&(n-c[x]>)) ans=std::min(ans,std::max(son[x],n-son[x]));

 }

 void sbpianfen(){

     ans=inf;

     Dfs(,);

     printf("%d\n",ans);

 }

 void insert(int x,int y){

     tot++;

     go[tot]=y;

     next[tot]=first[x];

     first[x]=tot;

     pass[tot]=;

 }

 void add(int x,int y){

     insert(x,y);op[tot]=tot+;insert(y,x);op[tot]=tot-;

 }

 void Insert(int x,int y){

     Tot++;

     Go[Tot]=y;

     Next[Tot]=First[x];

     First[x]=Tot;

 }

 void Add(int x,int y){

     Insert(x,y);Insert(y,x);

 }

 int bfs(int x){

     int h=,t=;

     bool ck=;

     c[]=x;vis[x]=;if (b[x]) ck=;

     while (h<=t){

         int now=c[h++];

         for (int i=First[now];i;i=Next[i]){

             int pur=Go[i];

             if (vis[pur]) continue;

             c[++t]=pur;

             vis[pur]=;

             if (b[pur]) ck=;

         }

     }

     if (!ck) pd=;

     return t;

 }

 void dFs(int x){

     if (x==n){

         pd=;

         int bl=;

         for (int i=;i<=n;i++)

          First[i]=;

         Tot=;

         for (int i=;i<n;i++)

          if (!e[i].id) Add(e[i].u,e[i].v);

         for (int i=;i<=n;i++)

           vis[i]=;

         for (int i=;i<=n;i++)

          if (!vis[i])

           bl=std::max(bl,bfs(i));

         if (pd==) ans=std::min(ans,bl);

         return;

     }

     e[x].id=;

     dFs(x+);

     e[x].id=;

     dFs(x+);

 }

 void sxpianfen(){

     for (int i=;i<n;i++) e[i].id=;

     dFs();

 }

 void clear(int x){

     int h=,t=;

     C[]=x;

     bool ppp=;

     if (b[x]) Cnt++,ppp=;

     vis[x]=;b[x]=;

     while (h<=t){

         int now=C[h++];

         for (int i=first[now];i;i=next[i]){

             int pur=go[i];

             if (pass[i]) continue;

             if (vis[pur]) continue;

             C[++t]=pur;

             vis[pur]=;

             if (b[pur]) Cnt++,ppp=;

             b[pur]=;

         }

     }

     if (ppp) {

         pd=;

         return;

     }

     if (t>block) pd=;

     sum-=t;

 }

 void work(int x,int mid,int fa,int Edge){

     if (c[x]==&&b[fa]==&&son[x]<=block) {

         pass[Edge]=;

         pass[op[Edge]]=;

         clear(x);

         id1=x;id2=fa;

         if (pd) return;

         return;

     }

     else

     if (k-Cnt-c[x]==&&b[x]==&&sum-son[x]<=block){

         pass[Edge]=;

         pass[op[Edge]]=;

         clear(fa);

         id1=x;id2=fa;

         if (pd) return;

         return;

     }

     else

     if (c[x]==&&son[x]<=block&&son[fa]>=block){

         pass[Edge]=;

         pass[op[Edge]]=;

         clear(x);

         id1=x;id2=fa;

         if (pd) return;

         return;

     }else

     if (k-Cnt-c[x]==&&sum-son[x]==block){

         pass[Edge]=;

         pass[op[Edge]]=;

         clear(fa);

         id1=x;id2=fa;

         if (pd) return;

         return;

     }

     for (int i=first[x];i;i=next[i]){

         int pur=go[i];

         if (pur==fa) continue;

         if (vis[pur]) continue;

         if (pass[i]) continue;

         work(pur,mid,x,i);

     }

 }

 bool check(int mid){

     for (int i=;i<n;i++) std::swap(e[rand()%(n-)+],e[rand()%(n-)+]);

     for (int i=;i<=n;i++) first[i]=;

     tot=;

     for (int i=;i<n;i++)

      add(e[i].u,e[i].v);

     block=mid;pd=;

     for (int i=;i<=tot;i++)

      pass[i]=;

     for (int i=;i<=n;i++)

      b[i]=B[i],vis[i]=;

     id1=;id2=;vis[]=;

     sum=n;Cnt=;

     for (int i=;i<=k;i++){

       if (vis[id1]&&vis[id2]) break;

       if (k-Cnt==) break;

       if (!vis[id1]){

        Dfs(id1,);

        work(id1,mid,,);

       }else{

        Dfs(id2,);

        work(id2,mid,,);

       }

       if (pd) return ;

     }

     for (int i=;i<=n;i++)

      if (!vis[i]) clear(i);

     if (pd) return ;

     return ;

 }

 void solve(){

     int l=n/k,r=n,Ans=n;

     while (l<=r){

         int mid=(l+r)/;

         if (check(mid)) r=mid-,Ans=mid;

         else l=mid+;

     }

     printf("%d\n",Ans);

 }

 void solve2(){

     int l=n/k,r=n,Ans=n;

     while (l<=r){

         int mid=(l+r)/;

         if (check(mid)) r=mid-,Ans=mid;

         else l=mid+;

     }

     int Tn=Ans;

     l=n/k,r=n,Ans=n;

     while (l<=r){

         int mid=(l+r)/;

         if (check(mid)) r=mid-,Ans=mid;

         else l=mid+;

     }

     Tn=std::min(Tn,Ans);

     printf("%d\n",Tn);

 }

 int main(){

     //♂

     freopen("deep.in","r",stdin);

     freopen("deep.out","w",stdout);

     srand(time(NULL));

     ans=inf;

     n=read();k=read();

     for (int i=;i<n;i++){

         int x=read(),y=read();

         add(x,y);

         e[i].u=x;e[i].v=y;

     }

     for (int i=;i<=k;i++){

         int x=read();

         b[x]=;B[x]=;

     }

     if (n<=) {sxpianfen();printf("%d\n",ans);return ;}

     if (k==) {printf("%d\n",n);return ;}

     if (k==) {sbpianfen();return ;}

     if (n<=) {solve();return ;}

     if (k==) {solve2();return ;}

     if (k==n) {printf("%d\n",);return ;}

     if (k==n-) {printf("%d\n",);return ;}

     solve();

 }

 #include<algorithm>

 #include<cstdio>

 #include<cmath>

 #include<cstring>

 #include<iostream>

 #define N 200005

 int tot,go[N*],next[N*],first[N];

 int n,k,b[N],fa[N],mx[N],sum[N],vis[N],c[N];

 int read(){

     char ch=getchar();int t=,f=;

     while (ch<''||ch>''){if (ch=='-') f=-;ch=getchar();}

     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}

     return t*f;

 }

 void insert(int x,int y){

     tot++;

     go[tot]=y;

     next[tot]=first[x];

     first[x]=tot;

 }

 void add(int x,int y){

     insert(x,y);insert(y,x);

 }

 void bfs(){

     int h=,t=;for (int i=;i<=n;i++) vis[i]=;

     c[]=;

     vis[]=;

     while (h<=t){

         int now=c[h++];

         for (int i=first[now];i;i=next[i]){

             int pur=go[i];

             if (vis[pur]) continue;

             vis[pur]=;

             c[++t]=pur;

             fa[pur]=now;

         }

     }

 }

 bool check(int mid){

     int f;

     memset(sum,,sizeof sum);

     memset(mx,,sizeof mx);

     for (int i=n;i>=;i--){

         int u=c[i];

         if (b[u]) mx[u]=mid-;

         else sum[u]++;

         f=(mx[u]>=sum[u])?mx[u]-sum[u]:-sum[u];

         if (u==&&f<) return ;

         if (f<) sum[fa[u]]-=f;

         else mx[fa[u]]=std::max(mx[fa[u]],f);

     }

     return ;

 }

 int main(){

     n=read();k=read();

     for (int i=;i<n;i++){

         int x=read(),y=read();

         add(x,y);

     }

     for (int i=;i<=k;i++){

         int x=read();

         b[x]=;

     }

     bfs();

     int l=n/k,r=n,ans;

     while (l<=r){

         int mid=(l+r)>>;

         if (check(mid)) r=mid-,ans=mid;

         else l=mid+;

     }

     printf("%d\n",ans);

 }