#include <bits/stdc++.h>

using namespace std;
ifstream in("apm.in");
ofstream out("apm.out");
const int NMAX=200003;
int n,m,father[NMAX],s[NMAX],costmin;
int Find(int node){
    if(father[node]==node)
        return node;
    return father[node]=Find(father[node]);
}
void Union(int a,int b){
    int fa=Find(a),fb=Find(b);
    if(fa==fb)
        return;
    if(s[fa]<s[fb])
        swap(fa,fb);
    father[fb]=fa;
    s[fa]+=s[fb];
}
struct edge{
    int a,b,cost;
    bool operator <(const edge&aux)const{
        return aux.cost>cost;
    }
};
vector<edge>v,rasp;
int main()
{
    in>>n>>m;
    for(int i=1;i<=n;i++)
        father[i]=i,s[i]=1;
    for(int i=1,a,b,cost;i<=m;i++){
        in>>a>>b>>cost;
        v.push_back({a,b,cost});
    }
    sort(v.begin(),v.end());
    for(auto y:v){
        int a=y.a,b=y.b,cost=y.cost;
        int fa=Find(a),fb=Find(b);
        if(fa==fb)
           continue;
        Union(a,b);
        rasp.push_back({a,b});
        costmin+=cost;
    }
    out<<costmin<<'\n';
    for(auto y:rasp)
        out<<y.a<<" "<<y.b<<'\n';
    return 0;
}