#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#define N 100005
#define INF 0x3f3f3f3f
#define ll long long
using namespace std;
int n, m, fa[N], cnt;
struct edge {
	int u, v, w;
	bool tag;
	bool operator < (const edge& t) const { return w < t.w; };
}e[N];

int find(int u) {
	return fa[u] == u ? u : fa[u] = find(fa[u]);
}
vector <edge> pre;
void clear() {
	for (int i = 1; i <= n; i++)
		fa[i] = i;
	cnt = 0;
}

struct node {
	int v, w;
};
vector <node> son[N];
int f[N][20], Max[N][20];


int dep[N], val[N];

void dfs(int u, int fa) {
	dep[u] = dep[fa] + 1;
	f[u][0] = fa;
	for (int i = 1; (1 << i) <= dep[u]; i++) {
		f[u][i] = f[f[u][i - 1]][i - 1];
	}
	for (int i = 0; i < son[u].size(); i++) {
		int v = son[u][i].v, w = son[u][i].w;
		if (v == fa) continue;
		val[v] = w;
		dfs(v, u);
	}
}

void fun(int u, int fa) {
	Max[u][0] = val[u];
	for (int i = 1; i <= 19; i++) {
		Max[u][i] = max(Max[ f[u][i - 1] ][i - 1], Max[u][i - 1]);
	}
	for (int i = 0; i < son[u].size(); i++) {
		int v = son[u][i].v;
		if (v != fa) fun(v, u);
	}
}
int get(int s, int t) {
	int res = -INF;
	if (dep[s] < dep[t]) swap(s, t);
	for (int i = 19; i >= 0; i--) {
		if (dep[s] - (1 << i) >= dep[t]) {
			res = max(res, Max[s][i]);
			s = f[s][i];
		}
	}
	if (s == t) return res;
	for (int i = 19; i >= 0; i--) {
		if (f[s][i] != f[t][i]) {
			res = max(res, max(Max[s][i], Max[t][i]) );
			s = f[s][i];
			t = f[t][i];
		}
	}
	return max(res, max(Max[s][0],Max[t][0]));
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	cin >> n >> m;

	for (int i = 1; i <= m; i++) {
		cin >> e[i].u >> e[i].v >> e[i].w;
		e[i].tag = 1;
	}
	sort(e + 1, e + m + 1);
	clear();
	for (int i = 1; i <= m; i++) {
		int u = e[i].u, v = e[i].v;
		int fu = find(u), fv = find(v);
		if (fu == fv) continue;
		fa[fv] = fu;
		e[i].tag = 0;
		pre.push_back(e[i]);
		cnt++;
		if (cnt == n - 1) break;
	}

	clear();
	for (int i = 1; i <= m; i++) {
		if (!e[i].tag) continue;
		int u = e[i].u, v = e[i].v;
		int fu = find(u), fv = find(v);
		if (fu == fv) continue;
		fa[fv] = fu;

		son[u].push_back({ v,e[i].w });
		son[v].push_back({ u,e[i].w });

		cnt++;
		if (cnt == n - 1) break;
	}
	if (cnt < n - 1) {
		cout << -1;
		return 0;
	}

	int rt = 1;
	dfs(rt, 0);
	val[rt] = -INF;
	fun(rt, 0);

	ll ans = 0;
	for (int i = 0; i < pre.size(); i++) {
		int s = pre[i].u, t = pre[i].v;
		//cout << s << " " << t << " " << pre[i].w << " ";
		ll tmp = (ll)get(s, t);
		//cout << tmp << " " << endl;
		ans += tmp + 1LL - pre[i].w;
	}
	cout << ans;
	return 0;
}