#include<fstream>
#include<algorithm>
#define NM 200100
using namespace std;
ifstream f("apm.in");
ofstream g("apm.out");
struct el{int x,y,c;}v[NM];
int i,n,m,GR[NM],t,sol[NM],S;
int cmp(el a,el b)
{
	return a.c<b.c;
}
int gr(int i)
{
	if(GR[i]==i) return i;
	GR[i]=gr(GR[i]);
	return GR[i];
}
void unite(int i,int j)
{
	GR[gr(i)]=gr(j);
}
int main ()
{
	f>>n>>m;
	for(i=1;i<=m;++i)
	{
		f>>v[i].x>>v[i].y>>v[i].c;
	}
	sort(v+1,v+m+1,cmp);
	for(i=1;i<=n;++i) GR[i]=i;
	for(i=1;i<=m;++i)
	{
		if(gr(v[i].x)!=gr(v[i].y))
		{
			S+=v[i].c;
			unite(v[i].x,v[i].y);
			sol[++t]=i;
		}
	}
	g<<S<<"\n";
	for(i=1;i<n;++i)
		g<<v[sol[i]].x<<" "<<v[sol[i]].y<<"\n";
	return 0;
}