#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize(2)
//#pragma GCC optimize(3, "Ofast", "inline")
#define hh putchar('\n')
#define kg putchar(' ')
#define debug puts("debug")
//#define int long long
//#define int __int128
namespace quickread{
	inline int read(){
		int x=0,f=1;char ch=getchar();
		while (ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
		while (ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
		return x*f;
	}
	inline void write(int x){
	    if(x<0){putchar('-');x=-x;}
	    if(x>9)write(x/10);
	    putchar(x%10+'0');
	}
	inline string readstr(){
    	char ch=getchar();string str="";
		while(!(ch>='0'&&ch<='9')&&!(ch>='a'&&ch<='z')&&!(ch>='A'&&ch<='Z')) ch=getchar();
		while((ch>='0'&&ch<='9')||(ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')){str+=ch;ch=getchar();}
		return str;
	}
	inline char readchar(){
		char ch=getchar();
		while(!(ch>='0'&&ch<='9')&&!(ch>='a'&&ch<='z')&&!(ch>='A'&&ch<='Z')) ch=getchar();
		return ch;
	}
}
using namespace quickread;
const int N=1e6+10;
int n,m,dis[N],ans;
bool vis[N];
struct edge{
	int v,w;
};
vector<edge>p[N],g[N];
struct csp{
	int u,w;
};
bool operator > (const csp& a,const csp& b){
	return a.w>b.w;
}
void dijkstra_p(int u){
	memset(dis,0x3f,sizeof(dis));memset(vis,0,sizeof(vis));
	dis[u]=0;
	priority_queue<csp ,vector<csp> ,greater<csp> >q;
	q.push(csp{u,0});
	while(!q.empty()){
		u=q.top().u;
		q.pop();
		if(vis[u]) continue;
		vis[u]=1;
		for(edge to:p[u]){
			int v=to.v,w=dis[u]+to.w;
			if(dis[v]>w){
				dis[v]=w;
				q.push(csp{v,w});
			}
		}
	}
	for(int i=2;i<=n;i++)
		ans+=dis[i];
}
void dijkstra_g(int u){
	memset(dis,0x3f,sizeof(dis));memset(vis,0,sizeof(vis));
	dis[u]=0;
	priority_queue<csp ,vector<csp> ,greater<csp> >q;
	q.push(csp{u,0});
	while(!q.empty()){
		u=q.top().u;
		q.pop();
		if(vis[u]) continue;
		vis[u]=1;
		for(edge to:g[u]){
			int v=to.v,w=dis[u]+to.w;
			if(dis[v]>w){
				dis[v]=w;
				q.push(csp{v,w});
			}
		}
	}
	for(int i=2;i<=n;i++)
		ans+=dis[i];
}
signed main(){
//	ios::sync_with_stdio(0);
//	cin.tie(0);cout.tie(0);
	n=read(),m=read();
	for(int i=1;i<=n;i++){
		int u=read(),v=read(),w=read();
		p[u].push_back(edge{v,w});
		g[v].push_back(edge{u,w});
	}
	dijkstra_p(1);
	dijkstra_g(1);
	write(ans);
	return 0;
}