#include <fstream>
#include <queue>
#include <vector>
using namespace std;
ifstream fin("apm.in");
ofstream fout("apm.out");
struct heap
{
    int node,father,cost;
}step;
struct cmp
{
    bool operator()(const heap &a,const heap &b)
    {
        return a.cost>b.cost;
    }
};
priority_queue<heap,vector<heap>,cmp> Q;
vector<pair<int,int> > H[200001];
vector<pair<int,int> > ::iterator it;
vector<pair<int,int> > edges;
bool used[200001];
int main()
{
    int n,m,a,b,i,c,totalcost=0,nod,cost;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b>>c;
        H[a].push_back(make_pair(b,c));
        H[b].push_back(make_pair(a,c));
    }
    for(it=H[1].begin();it!=H[1].end();it++)
    {
        step.node=it->first;
        step.cost=it->second;
        step.father=1;
        Q.push(step);
    }
    used[1]=1;
    for(i=2;i<=n;i++)
    {
        while(used[Q.top().node]!=0) Q.pop();
        nod=Q.top().node;
        cost=Q.top().cost;
        edges.push_back(make_pair(Q.top().father,Q.top().node));
        used[nod]=1;
        totalcost+=cost;
        for(it=H[nod].begin();it!=H[nod].end();it++)
        {
            if(used[it->first]==0)
            {
                step.father=nod;
                step.node=it->first;
                step.cost=it->second;
                Q.push(step);
            }
        }
    }
    fout<<totalcost<<"\n";
    for(it=edges.begin();it!=edges.end();it++) fout<<it->first<<" "<<it->second<<"\n";
}