prim

int n;
int weight;
int g[MAXN][MAXN];
int vis[MAXN];
int dis[MAXN];


void prim(int v0){
    int pos = v0;
    for(int i = 1; i <= n; i++){
        dis[i] = g[v0][i];
    }
    vis[pos] = 1;
    for(int i = 1; i < n; i++){
        int mins = INF;
        for(int j = 1; j <= n; j++){
            if(!vis[j] && dis[j] < mins){
                pos = j;
                mins = dis[j];
            }
        }
        weight += mins;
        vis[pos] = 1;
        for(int j = 1; j <= n; j++){
            if(!vis[j] && g[pos][j] < dis[j]){
                dis[j] = g[pos][j];
            }
        }
    }
}

#include <iostream>
#include <queue>
#include <string.h>
using namespace std;
#define M 1000
int g[M][M];
int n, cnt;
int node[M];
int weight;

void init(){
    memset(g,0,sizeof(g));
    memset(node,0,sizeof(node));
}

struct Edge{
    int from,to,w;
};

bool operator < (const Edge &a, const Edge &b){
    return a.w > b.w;
}

int prim(int start){
    node[start] = 1;
    priority_queue<Edge> q;
    for(int i = 0; i < n; i++){
        if(0 != g[start][i]){
            Edge e;
            e.from = start;
            e.to = i;
            e.w = g[start][i];
            q.push(e);
        }
    }
    while(!q.empty()){
        Edge cmp = q.top();
        q.pop();
        if(node[cmp.from] == 0 || node[cmp.to] == 0){
            node[cmp.from] = node[cmp.to] = 1;
            weight += cmp.w;
        }
        for(int i = 0; i < n; i++){
            if(node[i] == 0 && g[cmp.to][i] != 0){
                Edge add;
                add.from = cmp.to;
                add.to = i;
                add.w = g[cmp.to][i];
                q.push(add);
            }
        }
    }
}
int main(){
    init();
    cin >> n >> cnt;
    for(int i = 0; i < cnt; i++){
        int a, b, w;
        cin >> a >> b >> w;
        g[a][b] = g[b][a] = w;
    }
    prim(0);
    cout << weight << endl;
    return 0;
}