#include <bits/stdc++.h>

using namespace std;
ifstream f("apm.in");
ofstream g("apm.out");
int n, m;
int t[200001], r[200001];

struct edge{
  int cost, x, y;
};

vector<edge> edges;

bool cmp(edge edge1, edge edge2)
{
  return edge1.cost < edge2.cost;
}

void read()
{
  f>>n>>m;
  int x, y, z;
  for(int i = 1;i <= m;++i)
    f>>x>>y>>z, edges.push_back({z, x, y});
}

int found(int x)
{
  if(t[x] == x)
    return x;
  return t[x] = found(t[x]);
}

void unite(int x, int y)
{
  if(r[x] > r[y])
    t[y] = x, r[x] += r[y];
  else
    t[x] = y, r[y] += r[x];
}

void solve()
{
  for(int i = 1;i <= n;++i)
    r[i] = 1, t[i] = i;

  sort(edges.begin(), edges.end(), cmp);

  int cost = 0;
  vector<pair<int, int>> result;
  for(edge it : edges)
    if(found(it.x) != found(it.y))
      {
        cost += it.cost;
        unite(found(it.x), found(it.y));
        result.push_back(make_pair(it.x, it.y));
      }
  g<<cost<<'\n';
  for(auto it : result)
    g<<it.first<<" "<<it.second<<'\n';
}

int main()
{
  read();
  solve();
  return 0;
}