#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("apm.in");
ofstream g("apm.out");
int n,m,suma=0;
struct muchie
{
    int cap1;
    int cap2;
    int cost;
};
int l[100001], k[100001];
muchie mi[2000];
int tt[100001],rang[100001],nrcon=1;
int multime(int x)
{
    int R=x,y;
    while(tt[R]!=R) R=tt[R];
    while(tt[x]!=x)
    {
        y=tt[x];
        tt[x]=R;
        x=y;
    }
    return R;
}
int uniune(int x, int y)
{
    if(rang[x]>rang[y]) tt[y]=x;
    else tt[x]=y;
    if(rang[x]==rang[y]) rang[y]++;
}
void citire()
{
    f>>n>>m;
    for(int i=1; i<=2*m; i++)
    {
        f>>mi[i].cap1>>mi[i].cap2>>mi[i].cost;
        mi[i+1].cap1=mi[i].cap2;
        mi[i+1].cap2=mi[i].cap1;
        mi[i+1].cost=mi[i].cost;i++;
    }
}
bool compara(muchie x,muchie y)
{
    return x.cost<y.cost;
}
int main()
{
    citire();
    sort(mi, mi+2*m+1, compara);
    for(int i=1; i<=n; i++)
    {
        rang[i]=1;
        tt[i]=i;
    }
    for(int i=1; i<=2*m; i++)
    {
        if(nrcon<=n-1)
        {if(multime(mi[i].cap2)!=multime(mi[i].cap1))
        {
            suma+=mi[i].cost;
            uniune(multime(mi[i].cap2),multime(mi[i].cap1));
            l[nrcon]=mi[i].cap1;k[nrcon]=mi[i].cap2;
            nrcon++;
        }}
    }
    g<<suma<<'\n';
    for(int i=1;i<=nrcon-1;i++)
        g<<l[i]<<" "<<k[i]<<'\n';
    return 0;
}