#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#ifdef APURBA
#include "DEBUG_TEMPLATE.h"
#else
#define HERE
#define debug(args...)
#endif
#define ALL(x) x.begin(),x.end()
typedef pair<int,int> pii;
const int N = 3003;

struct DSU
{
    vector<int>parent;
    vector<int>rnk;
    int n;
    DSU(int nn)
    {
        n=nn;
        parent.resize(n);
        rnk.resize(n);
        for(int i=0; i<n; i++)
        {
            make_set(i);
        }
    }
    void make_set(int x)
    {
        rnk[x] = 0;
        parent[x] = x;
    }
    int find_set(int x)
    {
        if(parent[x]!=x)
        {
            parent[x] = find_set(parent[x]);
        }
        return parent[x];
    }
    void Union(int u,int v)
    {
        int p= find_set(u),q=find_set(v);
        if(p==q)
            return;
        if( rnk[p] > rnk[q])
            swap(p,q);
        parent[p]= q;
        if(rnk[p]==rnk[q])
        {
            rnk[q] +=1;
        }
    }
} dsu(N);
array<int,3> e[N];
map<int,int> cnt;
map<int,int> now;
map<int,vector<int> > eg;
set<pii> g[N];
bool ase[N];
bool mustrem[N];
vector<pii> es;
ll sum;
void calc(int n,int m,int ii)
{
    for(int i=1;i<=n;i++) dsu.make_set(i);
    ll s=0;
    {
        auto [u,v,w] = e[ii];
        dsu.Union(u,v);
        s+=w;
    }
    for(auto [_,i]: es)
    {
        auto [u,v,w] = e[i];

        if(dsu.find_set(u) != dsu.find_set(v))
        {
            dsu.Union(u,v);
            s+=w;
        }
    }
    mustrem[ii] = s != sum;
}


vector<pii> ans;
int ret;
bool paisi = 0;
bool gt(int u,int p,int t)
{
    if(u==t) return 1;

    for(auto [v,i]: g[u])
        if(v!=p)
    {
        if(gt(v,u,t))
        {
            auto &[uu,vv,ww] = e[i];
//            debug(i,now[ww],cnt[ww]);
            if(mustrem[i])
            {
                paisi=1;
                ret = i;
            }
            else if(!paisi and now[ww]>cnt[ww])
            {
                ret=max(ret,i);
            }
//            debug(ret);
            return 1;
        }
    }
    return 0;
}

void rep(int i)
{
    auto &[u,v,w] = e[i];
    ret=-1;
    paisi=0;
    debug(u,v,i,ret);
    assert(ase[i]==0);
    gt(u,-1,v);
    debug(ret,paisi);
    assert(ret!=-1);
    auto &[uu,vv,ww] = e[ret];
    assert(ase[ret]==1);
    g[uu].erase({vv,ret});
    g[vv].erase({uu,ret});
    g[u].insert({v,i});
    g[v].insert({u,i});
    now[ww]--;
    now[w]++;
    debug(w,now[w],ww,now[ww]);
    ase[ret]=0;
    ase[i]=1;
    ans.push_back({ret,i});
}



void TEST_CASES()
{
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        auto &[u,v,w] = e[i];
        cin>>u>>v>>w;
        if(i<=n-1)
        {
            g[u].insert({v,i});
            g[v].insert({u,i});
            now[w]++;
            ase[i]=1;
        }
        eg[w].push_back(i);
    }
    es=vector<pii> (m);
    for(int i=0;i<m;i++)
    {
        auto &[u,v,w] = e[i+1];
        es[i]={w,i+1};
    }
    sort(ALL(es));
    for(auto [_,i]: es)
    {
        auto &[u,v,w] = e[i];
        if(dsu.find_set(u)!=dsu.find_set(v))
        {
            debug(u,v,w);
            dsu.Union(u,v);
            cnt[w]++;
            sum+=w;
        }
    }
    debug(cnt);
    for(int i=1;i<=m;i++) calc(n,m,i);

    for(auto [w,x]: cnt)
    {
        int &y = now[w];
        assert(y<=x);
        debug(w,x,y);
        //if(y  == x) continue;
        for(int i: eg[w])
        {
            debug(x,i);
            if(x == y) break;
            if(ase[i]) continue;
            if(mustrem[i]) continue;
            rep(i);
        }
    }
    cout<<ans.size()<<"\n";
    for(auto [a,b]: ans) cout<<a<<" "<<b<<"\n";

}


/*
*/

int32_t main()
{
#ifndef APURBA
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#endif
    //freopen("input.txt","r",stdin);
    //freopen("out1.txt","w",stdout);
    int t=1;
    //cin>>t;
    while(t--)
    {
        TEST_CASES();
    }
    return 0;
}