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ccc16s3.cpp
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ccc16s3.cpp
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#include <bits/stdc++.h>
using namespace std;
vector<int> adj[1000000];
vector<bool> pho(1000000);
vector<bool> vis(1000000, 0);
vector<int> dis(1000000);
int n, m;
int far, totdist = 0;
bool x = 0;
void dfs(int src, int prev){
for (auto i: adj[src]){
if (i != prev){
dfs(i, src);
if (pho[i]) pho[src] = 1;
}
}
}
void bfs(int src){
totdist = 0;
queue<int> q;
int curr;
vector<bool> vis(1000000, 0);
dis[src] = 0;
vis[src] = 1;
q.push(src);
while (!q.empty()){
curr = q.front(); far = curr;
q.pop();
for (auto i: adj[curr]){
if (pho[i] && !vis[i]){
vis[i] = 1;
dis[i] = dis[curr] + 1;
totdist += 2;
q.push(i);
}
}
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
int num;
for (int i = 0; i < m; i++){
cin >> num;
pho[num] = 1;
}
for (int i = 1; i < n; i++){
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
dfs(num, -1);
//for (int i = 0; i < n; i++) cout << pho[i] << " ";
bfs(num);
bfs(far);
//cout << far << endl;
//cout << totdist << "\n";
int diameter = 0;
for (int i = 0; i < n; i++) {
if (pho[i]) diameter = max(diameter, dis[i]);
}
cout << totdist - diameter << "\n";
}