#include <fstream>
#include <queue>
#define NMAX 200001

using namespace std;
ifstream fin("apm.in");
ofstream fout("apm.out");
struct muchie
{
    int x, y;
    int cost;
    friend bool operator >(const muchie&, const muchie&);
};
bool operator >(const muchie& m1, const muchie& m2)
{
    return m1.cost>m2.cost;
}
priority_queue<muchie, vector<muchie>, greater<muchie> > H;
vector<muchie> sol;
int tata[NMAX];
int h[NMAX];
int n;
double costmin;
void citire();
void afisare();
void Union(int x, int y)
{
    if (h[x]>h[y])
        tata[y]=x;
    else
    {
        if (h[x]==h[y]) h[y]++;
            tata[x]=y;
    }
}
int Find(int x)
{
    int rad=x, y, t;
    while (tata[rad])
        rad=tata[rad];
    y=x;
    while (y!=rad)
    {
        t=tata[y];
        tata[y]=rad;
        y=t;
    }
    return rad;
}

int main()
{
    int c1, c2;
    muchie m;
    citire();
    while (sol.size()<n-1)
    {
        m=H.top(); H.pop();
        c1=Find(m.x); c2=Find(m.y);
        if (c1!=c2)
        {
            costmin+=m.cost; sol.push_back(m);
            Union(c1, c2);
        }
    }
    afisare();
    return 0;
}
void citire()
{
    muchie m;
    int i, nrm;
    fin>>n>>nrm;
    for (i=0; i<nrm; i++) {fin>>m.x>>m.y>>m.cost; H.push(m);}
}
void afisare()
{
    fout<<costmin<<'\n';
    for (int i=0; i<n-1; i++) fout<<sol[i].x<<" "<<sol[i].y<<'\n';
}