#include <bits/stdc++.h>

#define MaxN     200005
#define inf      (int)(2e9+5)
#define int_pair std::pair <int, int>
#define mp       std::make_pair

std::ifstream InFile("apm.in");
std::ofstream OutFile("apm.out");

int N, M, Ans;
std::map <int, int> Edge[MaxN];
std::vector <int_pair> ADC[MaxN];

int Parent[MaxN],
    Key[MaxN];
bool InMST[MaxN];
void Prim(int Source = 1) {
    for (int i=0; i<N; ++i)
        Parent[i+1] = 0,
        Key[i+1] = inf;

    struct PrimData {
        int Value;

        bool operator < (const PrimData &Other) const {
            return Key[Value] > Key[Other.Value];
        }
    };  std::priority_queue <PrimData> PQ;

    PQ.push({Source});
    Key[Source] = 0;

    int Top;
    while (!PQ.empty()) {
        Top = PQ.top().Value;
        PQ.pop();

        InMST[Top] = 1;

        for (auto Edge:ADC[Top]) {
            if (!InMST[Edge.first] && Key[Edge.first] > Edge.second)
                Key[Edge.first] = Edge.second,
                Parent[Edge.first] = Top,
                PQ.push({Edge.first});
        }
    }
}

void Citire() {
    InFile >> N >> M;

    for (int i=0, x, y, c; i<M; ++i)
        InFile >> x >> y >> c,
        ADC[x].push_back(mp(y, c)),
        ADC[y].push_back(mp(x, c)),
        Edge[x][y] = c;
}

void Rezolvare() {
    Prim();

    int Sum = 0;
    for (int i=0; i<N; ++i)
        Sum += Key[i+1];
    OutFile << Sum << '\n';

    for (int i=0; i<N; ++i)
        if (Parent[i+1])
            OutFile << i+1 << ' ' << Parent[i+1] << '\n' ;
}

int main()
{
    Citire();
    Rezolvare();
    return 0;
}