#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

ifstream f("apm.in");
ofstream g("apm.out");

struct inf{
    int x, y, c;
};

int n, m;
int t[200005], rang[200005];
long long sum;
vector <inf> v;
vector <pair <int, int> > z;

bool cmp(inf a, inf b)
{
    return a.c <= b.c;
}

int rad(int nod)
{
    if(t[nod]==0)
        return nod;
    else
    {
        int aux=rad(t[nod]);
        t[nod]=aux;
        return aux;
    }
}

void unire(int a, int b)
{
    int ra=rad(a), rb=rad(b);
    if(ra!=rb)
    {
        if(rang[ra] > rang[rb])
            t[rb]=ra;
        else{
            t[ra]=rb;
            if(rang[ra]==rang[rb])
                rang[rb]++;
        }
    }
}

int main()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int a, b, cost;
        inf aux;
        f>>a>>b>>cost;
        aux.x=a;
        aux.y=b;
        aux.c=cost;
        v.push_back(aux);
    }
    sort(v.begin(), v.end(), cmp);
    int i=0;
    while(n>1)
    {
        int a=v[i].x;
        int b=v[i].y;
        int cost=v[i].c;
        int ra=rad(a);
        int rb=rad(b);
        if(ra!=rb)
        {
            unire(ra, rb);
            z.push_back(make_pair(a, b));
            n--;
            sum+=cost;
        }
        i++;
    }
    g<<sum<<'\n';
    for(auto elem:z)
        g<<elem.first<<" "<<elem.second<<'\n';
    return 0;
}