#include<bits/stdc++.h>
using namespace std;
const int maxn=2000010,inf=INT_MAX;
struct Edge {
	long long to,next,w;
} edge[maxn];
Edge edge1[maxn];
long long dis[maxn],p[maxn],vis[maxn],edge_num,edge_num1,dis1[maxn],p1[maxn],vis1[maxn];
int n,m;
void add_edge(int u,int v,int w) {
	edge[++edge_num].next=p[u];
	edge[edge_num].to=v;
	edge[edge_num].w=w;
	p[u]=edge_num;
}
void add_edge1(long long u,long long v,long long w) {
	edge1[++edge_num1].next=p1[u];
	edge1[edge_num1].to=v;
	edge1[edge_num1].w=w;
	p1[u]=edge_num1;
}

void dijkstra() {
	priority_queue<pair<long,long> >que;
	memset(vis,1,sizeof(vis));
	for(long long i=1; i<=n; i++)
		dis[i]=inf;

	dis[1]=0;
	vis[1]=0;

	que.push(make_pair(0,1));
	while(!que.empty()) {
		int x=que.top().second;
		que.pop();
		for(long long i=p[x]; i; i=edge[i].next) {
			long long tmp=edge[i].to;
			if(dis[tmp]>dis[x]+edge[i].w) {
				dis[tmp]=dis[x]+edge[i].w;
				que.push(make_pair(-dis[tmp],tmp));
			}
		}
	}
}
void dijkstra1() {
	priority_queue<pair<int,int> >que1;
	memset(vis1,1,sizeof(vis1));
	for(long long i=1; i<=n; i++)
		dis1[i]=inf;

	dis1[1]=0;
	vis1[1]=0;

	que1.push(make_pair(0,1));
	while(!que1.empty()) {
		long long x=que1.top().second;
		que1.pop();
		for(long long i=p1[x]; i; i=edge1[i].next) {
			long long tmp=edge1[i].to;
			if(dis1[tmp]>dis1[x]+edge1[i].w) {
				dis1[tmp]=dis1[x]+edge1[i].w;
				que1.push(make_pair(-dis1[tmp],tmp));
			}
		}
	}
}
int main() {
	cin>>n>>m;
	memset(p,0,sizeof(p));
	while(m--) {
		long long u,v,w;
		cin>>u>>v>>w;
		add_edge(u,v,w);
		add_edge1(v,u,w);
	}
	dijkstra();
	dijkstra1();
	long long cnt=0;
	for(int i=1; i<=n; i++)
		cnt+=dis[i]+dis1[i];
	cout<<cnt<<endl;
	return 0;
}