#include <iostream>
#include <vector>
#include <random>
#include <algorithm>
#include <list>
#include <cassert>
#include <queue>
#include <fstream>
using namespace std;

typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<pair<int,int>> VII;
typedef vector<vector<int>> VVI;
typedef vector<vector<pair<int,int>>> VVP;

class DisjointSet {
public:
    vector<int> parent, size;
    DisjointSet(int n) {
        parent = vector<int>(n);
        size = vector<int>(n);
        for (int i=0;i<n;i++) {
            parent[i] = i;
            size[i] = 1;
        }
    }

    int find(int x) {
        if (parent[x]==x) return x;
        int root = find(parent[x]);
        parent[x]=root;
        return root;
    }

    void join(int x, int y) {
        x=find(x); y=find(y);
        if (size[x]<size[y]) swap(x,y);
        parent[y]=x;
        size[x]+=size[y];
    }
};

int Kruskal(int n, vector<VI> &edges, vector<PII> &mst) {
    sort(edges.begin(),edges.end());
    DisjointSet ds(n);
    int cost=0;
    for (auto e : edges) {
        int a=e[1], b=e[2], w=e[0];
        if (ds.find(a)==ds.find(b)) continue;
        ds.join(a,b);
        mst.push_back({a,b});
        cost+=w;
    }
    return cost;
}

int main() {
    ifstream fin("mst.txt");
    int n,m;
    fin >> n >> m;
    vector<VI> edges;
    for (int i=0;i<m;i++) {
        int a,b,c;
        fin >> a >> b >> c;
        edges.push_back({c,a,b});
    }
    vector<PII> mst;
    cout << Kruskal(n,edges,mst) << endl;
    for (auto e : mst) {
        cout << e.first << " " << e.second << endl;
    }

    /*
    DisjointSet ds(10);
    ds.join(3,4); ds.join(5,7); ds.join(3,7);
    for (int i=0;i<10;i++) {
        cout << i << ": " << ds.find(i) << endl;
    }
    */
    return 0;
}