#include<stdio.h>    //大概要这些头文件

 #include<string.h>

 #include<queue>

 #include<vector>

 #include<algorithm>

 using namespace std;

 typedef pair<int,int> pii;

 int head[],next[],point[],val[],size,dist[];    //前向星及dist数组

 bool vis[];

 void add (int a,int b, int v){    //加边及去重

     int i;

     for(i=head[a];~i;i=next[i]){

         if(point[i]==b){

             if(val[i]>v)val[i]=v;

             return;

         }

     }

     point[size]=b;

     val[size]=v;

     next[size]=head[a];

     head[a]=size++;

 }

 struct cmp{    //重载小根堆

     bool operator()(pii a,pii b){

         return a.first>b.first;

     }

 };

 void prim(int s){    //prim函数，传入图中一点

     int i,ans=;

     memset(dist,-,sizeof(dist));

     memset(vis,,sizeof(vis));

     priority_queue<pii,vector<pii>,cmp>q;

     for (i=head[s];~i;i=next[i]){

         dist[point[i]]=val[i];

         q.push(make_pair(dist[point[i]],point[i]));

     }

     dist[s]=;

     vis[s]=;

     while(!q.empty()){

         pii u=q.top();

         q.pop();

         if(vis[u.second])continue;

         vis[u.second]=;

         ans+=u.first;

         for(i=head[u.second];~i;i=next[i]){

             int j=point[i];

             if(!vis[j]&&(dist[j]>val[i]||dist[j]==-)){

                 dist[j]=val[i];

                 q.push(make_pair(dist[j],j));

             }

         }

     }

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

 }