#include <iostream>
#include <fstream>
#include <algorithm>
#define DM 200005
using namespace std;
ifstream fin("apm.in");
ofstream fout("apm.out");

int n, m, a, b, c, dad[DM], cost_total, dim;
struct muchie {int x, y, cost;};
muchie g[DM], arb[DM];


bool cmp(muchie a, muchie b)
{
    return a.cost < b.cost;
}
int root(int nod)
{
    if(dad[nod] == nod)
        return nod;
    return dad[nod] = root(dad[nod]);
}
void unite(int x, int y)
{
    dad[root(x)] = root(y);
}
int main ()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        fin >> a >> b >> c;
        g[i] = {a, b, c};
    }
    sort(g + 1, g + m + 1, cmp);

    for(int i = 1; i <= n; i++)
        dad[i] = i;
    for(int i = 1; i <= m; i++)
    {
        a = g[i].x;
        b = g[i].y;
        c = g[i].cost;
        if(root(a) != root(b))
        {
            unite(a, b);
            arb[++dim] = {a, b, c}; // aici nu ne pasa de cost oricum
            cost_total += c;
        }
    }
    fout << cost_total << '\n';
    for(int i = 1; i <= dim; i++)
        fout << arb[i].x << ' ' << arb[i].y << '\n';

    return 0;
}