1 #include <iostream>
  2 #include <cstdio>
  3 #include <algorithm>
  4 #include <cstring>
  5 using namespace std;
  6  int n,m,s,e,tot;
  7  int dis[100001],toit[100001],cost[100001],next[100001],lists[100001],q[100001];
  8  bool flag[100001];
  9  #define maxint int(1e+9)
 10 struct point
 11 {
 12     int to,next;
 13 }
 14     edge[10000000];
 15     int head[510000],idx=0;
 16     bool vis[510000];
 17 struct anspoint
 18 {
 19     int to,next,num;
 20 }    
 21     ansedge[10000000];
 22     int anshead[510000],ansidx=0,ans[5100000],group[510000];
 23 void adds(int a,int b,int c)
 24 { 
 25     tot++;
 26     toit[tot]=b;
 27     cost[tot]=c;
 28     next[tot]=lists[a];
 29     lists[a]=tot;
 30 }
 31 void spfa(int s)//spfa
 32 {
 33      int i,head,tail,v,k;
 34     memset(flag,true,sizeof(flag));
 35     for (i=1;i<=n;i++)
 36       dis[i]=maxint;
 37     head=tail=1;
 38     q[1]=s; dis[s]=0; flag[s]=false;
 39     while (head<=tail) {
 40         v=q[head];
 41         k=lists[v];
 42         while (k!=0) {
 43           if (dis[v]+cost[k]<dis[toit[k]] ){
 44               dis[toit[k]]=dis[v]+cost[k];
 45               if( flag[toit[k]] ){
 46                   tail++;
 47                   q[tail]=toit[k];
 48                   flag[toit[k]]=false;
 49                   
 50               }
 51           }
 52           k=next[k];
 53         }
 54         flag[v]=true;
 55         head++;
 56     }    
 57 }
 58 void add(int u,int v)
 59 {
 60     edge[++idx].to=v;
 61     edge[idx].next=head[u];
 62     head[u]=idx;
 63 }
 64 void ansadd(int u,int v,int num)
 65 {
 66     ansedge[++ansidx].to=v;
 67     ansedge[ansidx].next=anshead[u];
 68     ansedge[ansidx].num=num;
 69     anshead[u]=ansidx;
 70 }
 71 int find(int x)
 72 {
 73     int pre=x,y;
 74     while (x!=group[x])
 75       x=group[x];
 76       while (pre!=group[pre])
 77       {
 78           y=group[pre];
 79           group[pre]=x;
 80           pre=y;
 81       }
 82     return x;
 83 }
 84 void tarjan(int x)//tarjan 离线求lca
 85 {
 86     vis[x]=1;
 87     group[x]=x;
 88     for (int i=head[x];i!=-1;i=edge[i].next)
 89     {
 90         int now=edge[i].to;
 91         if (!vis[now])
 92             {
 93                 tarjan(now);
 94                 group[now]=x;
 95             }
 96     }
 97     for (int i=anshead[x];i!=-1;i=ansedge[i].next)
 98     {
 99         int now=ansedge[i].to,num=ansedge[i].num;
100         if (vis[now])ans[num]=find(now);
101     }
102     }
103 //}
104 int main()
105 {
106       memset(head,-1,sizeof(head));
107       memset(anshead,-1,sizeof(anshead));
108       int x,y,anss;
109       int p[10000];
110       scanf("%d",&n);
111       for (int i=1;i<n;++i)
112       {
113           scanf("%d%d",&x,&y);
114           add(x,y); add(y,x);
115           adds(x,y,1); adds(y,x,1);
116       }
117       scanf("%d",&m);
118       for (int i=1;i<=m;++i)
119         scanf("%d",&p[i]);
120      for (int i=1;i<=m;++i)
121      {
122          if (i!=m ){
123          ansadd(p[i],p[i+1],i);
124          ansadd(p[i+1],p[i],i);
125      }
126       } 
127     tarjan(1);//从根节点开始
128     spfa(1);
129     anss=0;
130     for (int i=1;i<m;i++)
131     { 
132       //printf("%d\n",dis[p[i]]+dis[p[i+1]]-(2*dis[ans[i]]));
133         anss=anss+dis[p[i]]+dis[p[i+1]]-(2*dis[ans[i]]);
134     }
135       printf("%d\n",anss);
136 }
137