B. COVID-19 Outbreak (Toph)

#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef pair<int,int> pii;
typedef vector< pii > vii;

#define ll          long long
#define ff          first
#define ss          second
#define pb          push_back
#define mkp         make_pair
#define sz          size()

#define forf(a,b,c)    for(int i=a;i<=b;i+=c)
#define forr(a,b,c)    for(int i=a;i>=b;i-=c)
#define all(a)      a.begin(),a.end()
#define mem(a,b)    memset(a,b,sizeof(a))
#define pi          2*acos(0.0)
#define End         return 0;

#define scan1(a)    scanf("%d",&a)
#define scan2(a,b)  scanf("%d %d",&a,&b)
#define scan3(a,b,c)  scanf("%d %d %d",&a,&b,&c)
#define scanl(a)    scanf("%lld",&a)
#define scanll(a,b) scanf("%lld %lld",&a,&b)
#define scanlll(a,b,c) scanf("%lld %lld %lld",&a,&b,&c)

#define print1(a)    printf("%d",a)
#define print2(a,b)  printf("%d %d",a,b)
#define print3(a,b,c)  printf("%d %d %d",a,b,c)
#define printl(a)    printf("%lld",a)
#define printll(a,b) printf("%lld %lld",a,b)
#define printlll(a,b,c) printf("%lld %lld %lld",a,b,c)

#define MAXN        100000007
#define INF 0x3f3f3f3f

struct com{
    ll node;
    ll cost;
};
vector<vector<com> >adj(1000000+1);
bool vis[1000003];
ll truck[1000003];

ll dfs(ll src, ll trc){

    vis[src]=1;
    ll total=truck[src];
    for(int i=0;i<adj[src].sz;i++){
        ll t=adj[src][i].node;
        if(vis[t]==0) {
            total+=dfs(t,adj[src][i].cost);
        }
    }
    return min(total,trc);
}
int main()
{
   ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

   int n,z; cin>>n>>z;



   for(int i=0;i<n-1;i++){
    int a,b,y; cin>>a>>b>>y;
    adj[a].pb({b,y});
    adj[b].pb({a,y});
   }
   for(int i=1;i<=n;i++){
    cin>>truck[i];
   }

   cout<<dfs(z,10000000000000)<<endl;
   End;

}