package com.PTA.graph.Prim;
import java.util.Scanner;
public class Prim {
static Scanner cin = new Scanner(System.in);
static int Nv, Ne;
static int[][] G;
static void BuildGraph(){
Nv = cin.nextInt();
Ne = cin.nextInt();
G = new int[Nv+1][Nv+1];
for (int i = 1; i <= Nv; i++){
for (int j = 1; j <= Nv; j++){
G[i][j] = Integer.MAX_VALUE;
}
}
for (int i = 1; i <= Ne; i++){
int v1 = cin.nextInt(), v2 = cin.nextInt();
int w = cin.nextInt();
G[v1][v2] = w;
G[v2][v1] = w;
}
}
public static int distMin(int[] dist, boolean[] visited){
int min = Integer.MAX_VALUE;
int minV = 0;
for(int v = 1; v <= Nv; v++){
if(visited[v] == false && dist[v] < min){
min = dist[v];
minV = v;
}
}
if(min < Integer.MAX_VALUE){
return minV;
}else {
return -1;
}
}
public static void prim(){
boolean[] visited = new boolean[Nv+1];
int[] dist = new int[Nv+1];
int[] path = new int[Nv+1];
int sum = 0;
int vCount = 0;
for (int i = 1; i <= Nv; i++) {
path[i] = 1;
dist[i] = G[1][i];
}
visited[1] = true;
dist[1] = 0;
while (true){
int v = distMin(dist, visited);
if (v == -1){
break;
}
sum += G[v][path[v]];
visited[v] = true;
vCount++;
for (int i = 1; i <= Nv; i++) {
if (G[v][i] < dist[i] ) {
dist[i] = G[v][i];
path[i] = v;
}
}
}
if (vCount == (Nv-1))
System.out.println(sum);
else System.out.println("-1");
}
public static void main(String[] args) {
BuildGraph();
prim();
}
}