#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("apm.in");
ofstream out("apm.out");
int ct;
struct muchie {
    int x,y,c,ok;
}mch[400001];
bool comp(muchie a, muchie b)
{
    return a.c<b.c;
}
int main()
{
    int cx,cy,n,m,i,k[200001],j;
    in>>n>>m;
    for(i=1;i<=m;i++)
    {
        in>>mch[i].x>>mch[i].y>>mch[i].c;
    }
    for(i=1;i<=n;i++)
    {
        k[i] = i;
    }
    sort(mch+1,mch+m+1,comp);
    for(i=1,j=1;i<n;j++)
    {
        if(k[mch[j].x] != k[mch[j].y])
        {
            ct+=mch[j].c;
            mch[j].ok = 1;
             cx = k[mch[j].x];
             cy = k[mch[j].y];

        for(int ind=1;ind<=n;ind++)
        {
            if(k[ind] == cy)
                k[ind] = cx;
        }
            i++;
        }

    }
    out<<ct<<endl;
    for(i=1;i<=m;i++)
    {
        if(mch[i].ok == 1)
        {
            out<<mch[i].x<<" "<<mch[i].y<<endl;
        }
    }
}