…调半天别的东西写错了，心力交瘁。
思路还是不会。。
具体就是二分，没想到，然后再贪心。
一直没整明白一个数它要往别的树走的条件是什么，日后研究。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <set> 
#include <vector> 
#include <queue>#define mid (l+r>>1)
using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
typedef pair<LL,int>  PLI;
const int N = 5e4+10, mod=1e9+7;LL fa[N][20], le[N][20], deep[N], D; // deep i 到 1 的距离 
vector<PII>G[N];
vector<int> li;
vector<LL>C, B, A; 
int P[N], k, n;
bool dis[N];void dfs(int u, int f) // st 表  
{for(int i = 1;i < 20;i ++)fa[u][i] = fa[fa[u][i-1]][i-1], le[u][i] = le[u][i-1] + le[fa[u][i-1]][i-1]; for(auto x : G[u]){int a = x.first;if(a == f)continue;fa[a][0] = u; le[a][0] = x.second;deep[a] = deep[u] + x.second;	dfs(a, u);}	
}int se(int u, LL len) // u 走 len 最多走到哪. 
{for(int i = 19;i >= 0;i --)if(le[u][i] <= len) len -= le[u][i], u = fa[u][i];return u;	
}void dfs2(int u, int fa)
{if(dis[u] || (G[u].size() == 1&& u != 1)) return ;dis[u] = 1;for(auto x : G[u]){int a = x.first;if(a == fa)continue;dfs2(a, u);dis[u] &= dis[a]; }return ;
}bool check(LL len)  // ch函数 
{C.clear(); B.clear(); A.clear();
//	cout<<len<<endl; D = len;for(int i = 1;i <= n;i ++) dis[i] = 0;for(int i = 1;i <= k;i ++) {int x = se(P[i], len);if(x == 1) C.push_back(P[i]);else dis[x] = 1;}dfs2(1, 0);sort(C.begin(), C.end(), [](int a, int b){return D - deep[a] < D - deep[b];}) ;for(auto x : C){int a = se(x, deep[x]-1);if(!dis[a]&&len-deep[x]<=deep[a])dis[a] = 1;else A.push_back(len - deep[x]);}	
//	for(int i = 1;i <= n;i ++)cout<<dis[i]<<' ';cout<<endl;for(auto i:li) if(!dis[i]) B.push_back(deep[i]);//	for(auto x:A)cout<<x<<' ';cout<<endl;
//	for(auto x:B)cout<<x<<' ';cout<<endl;sort(B.begin(), B.end());sort(A.begin(), A.end());int now = 0, siz = A.size();for(auto x : B){while(now != siz && A[now] < x) now ++;if(now == siz)return 0;now ++;}return 1;
}int main()
{	scanf("%d", &n);for(int i = 2;i <= n;i ++){int a, b, c;scanf("%d%d%d", &a, &b, &c);if(a > b)swap(a, b);G[a].push_back({b, c});G[b].push_back({a, c});if(a == 1) li.push_back(b);}for(int i = 0;i < 20;i ++) le[1][i] = 0x3f3f3f3f3f3f3f3f;dfs(1, 0);  // st 初始化； sort(li.begin(), li.end(), [](int a, int b){return deep[a] < deep[b];});scanf("%d", &k);for(int i = 1;i <= k;i ++)scanf("%d", P+i);LL l = 0, r = 1e14;  // 二分答案 while(l < r){if(check(mid)) r = mid;else l = mid+1;}if(k < li.size()) l = -1;printf("%lld\n", l);return 0;
}