#include <bits/stdc++.h>
#define INF (1 << 30)
using namespace std;
int t, n, m, x, y, sum, cnt, t1, t2, t3, flag;
int mp[10005][10005], vis[10005], dis[10005];
void Prim() {
for(int i = 1; i <= n; i++) {
dis[i] = mp[1][i];
}
memset(vis, 0, sizeof(vis));
sum = cnt = 0;
vis[1] = 1;
cnt++;
for(int i = 2; i <= n; i++) {
int mindis = INF, k;
for(int j = 1; j <= n; j++) {
if(!vis[j] && dis[j] < mindis) {
mindis = dis[j];
k = j;
}
}
if(mindis == INF) {
flag = 1;
return;
}
vis[k] = 1;
sum += mindis;
for(int j = 1; j <= n; j++) {
if(!vis[j] && dis[j] > mp[k][j]) {
dis[j] = mp[k][j];
}
}
}
}
int main() {
while(~scanf("%d%d", &n, &m)) {
//初始化
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= n; j++) {
if(i == j) {
mp[i][j] = 0;
} else {
mp[i][j] = INF;
}
}
}
//读入边
for(int i = 1; i <= m; i++) {
scanf("%d%d%d", &t1, &t2, &t3);
if(t3 < mp[t1][t2]) {
mp[t1][t2] = mp[t2][t1] = t3;
}
}
//初始化dis数组
flag = 0;
Prim();
if(!flag) {
printf("%d\n", sum);
} else {
printf("-1\n");
}
}
return 0;
}