#include<bits/stdc++.h>
using namespace std;
const int maxn=(10+1e6)*2,INTMAX=0x3f3f3f3f,maxm=(1e6+10)*2;
int n,m;
struct E{
	int to,next,val;
}edge[maxn];
int head_1[maxm],head_2[maxm];

struct T{
	long long num,val;
	T(){}
	T(long long a,long long b){num=a,val=b;}
};
bool operator <(const T a,const T b){
	return a.val>b.val;
}

int len=1;
void read(){
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		int from,to,val;
		scanf("%d%d%d",&from,&to,&val);
		if(from==to) continue;
		edge[len].to=to;
		edge[len].val=val;
		edge[len].next=head_1[from];
		head_1[from]=len;
		len++;
		edge[len].to=from;
		edge[len].val=val;
		edge[len].next=head_2[to];
		head_2[to]=len;
		len++;
	}
}

bool vis[maxm];
long long dis_1[maxm];
long long dis_2[maxm];
void work(int s){
	memset(dis_1,0x3f,sizeof dis_1);
	priority_queue<T> q;
	dis_1[s]=0;
	q.push(T(s,0));
	while(!q.empty()){
		T p=q.top();q.pop();
		if(vis[p.num]) continue;
		vis[p.num]=1;
		long long num=p.num,diss=p.val;
		for(int i=head_1[num];i;i=edge[i].next){
			long long num_=edge[i].to,diss_=edge[i].val;
			if(vis[num_]) continue;
			if(dis_1[num_]>diss+diss_){
				q.push(T(num_,diss+diss_));
				dis_1[num_]=diss+diss_;
			}
		}
	}
	memset(dis_2,0x3f,sizeof dis_2);
	memset(vis,0,sizeof vis);
//	priority_queue<T> q;
	dis_2[s]=0;
	q.push(T(s,0));
	while(!q.empty()){
		T p=q.top();q.pop();
		if(vis[p.num]) continue;
		vis[p.num]=1;
		long long num=p.num,diss=p.val;
		for(int i=head_2[num];i;i=edge[i].next){
			long long num_=edge[i].to,diss_=edge[i].val;
			if(vis[num_]) continue;
			if(dis_2[num_]>diss+diss_){
				q.push(T(num_,diss+diss_));
				dis_2[num_]=diss+diss_;
			}
		}
	}
}

void P(){
	long long ans=0;
	for(int i=1;i<=n;i++){
		ans+=dis_1[i];
		ans+=dis_2[i];
//		cout<<dis_1[i]<<" "<<dis_2[i]<<endl;
	}
	printf("%lld\n",ans);
}

int main (){
	freopen("P1342_1 (1).in","r",stdin);
	read();
	work(1);
	P();
}