// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#include<bits/stdc++.h>
  
using namespace std;
  
#define i64 long long
#define int long long
#define mp make_pair
#define pb push_back
#define all(x) (x).begin(), (x).end()
  
const int MAXN = 5e5 + 5;
const i64 INF = LLONG_MAX/2;
struct DSU{
  int N, ccp;
  vector<int> lab, sz;
  vector<int64_t> sum;
  DSU(int _N) : N(_N), ccp(_N), sum(N + 5, 0), sz(_N + 5, 1), lab(_N + 5) {
    for (int i = 1; i <= N; i ++) {
      lab[i] = i;
    }
  }; 
  int findLab(int u) { return (u == lab[u] ? u : lab[u] = findLab(lab[u])); }
  bool unite(int u, int v, int64_t w) {
    int labu = findLab(u);
    int labv = findLab(v);
    if (labu == labv) return false;
    if (sz[labu] < sz[labv]) swap(labu, labv);
    sz[labu] += sz[labv];
    lab[labv] = labu;
    sum[labu] += sum[labv] + w;
    ccp --;
    return true;
  }
};
int N, M;
struct Edge {
  int u, v, w, id;
};
void Solve(void) {
  cin >> N >> M;
  vector<Edge> edges;
  vector<bool> used(M + 2, false);
  for (int i = 1; i <= M; i ++) {
    int u, v, w; cin >> u >> v >> w;
    edges.pb({u, v, w, i});
  }
  sort(all(edges), [&](Edge &a, Edge &b) {
    return a.w < b.w;
  });
  DSU MST(N);
  for (auto [u, v, w, id] : edges) {
    if (MST.unite(u, v, w)) {
      used[id] = true;
    }
  }
  int root = MST.findLab(1);
  i64 add = MST.sum[root];
  DSU NMST(N);
  for (auto [u, v, w, id] : edges) {
    if (used[id]) continue;
    if (NMST.unite(u, v, w)) {
    }
  }
  root = NMST.findLab(1);
  if (NMST.ccp != 1) {
    cout << -1 << "\n";
    return;
  }
  add = NMST.sum[root] - add + N - 1;
  cout << add << "\n";
}
signed main() {
  ios_base::sync_with_stdio(false); cin.tie(0);
  cout << fixed << setprecision(10);
  int Tests = 1; // cin >> Tests; 
  while (Tests --) {
    Solve();    
  }
}