#include<cstdio>
#include<iostream>
#include<set>
#include<vector>
#include<array>
#include<algorithm>
#define RI register int
#define CI const int&
#define fi first
#define se second
using namespace std;
typedef pair <int,int> pi;
const int N=3005;
int n,m,x[N],y[N],z[N],in[N],pre[N]; pi lst[N]; multiset <array <int,3>> v[N];
inline void addedge(CI id)
{
    v[x[id]].insert({y[id],z[id],id});
    v[y[id]].insert({x[id],z[id],id});
}
inline void deledge(CI id)
{
    v[x[id]].erase(v[x[id]].find({y[id],z[id],id}));
    v[y[id]].erase(v[y[id]].find({x[id],z[id],id}));
}
inline void find_path(CI now)
{
    for (auto [to,w,id]:v[now]) if (pre[to]==0)
    pre[to]=now,lst[to]={w,id},find_path(to);
}
int main()
{
    scanf("%d%d",&n,&m);
    vector <pi> E,ans;
    for (RI i=1;i<=m;++i)
    {
        scanf("%d%d%d",&x[i],&y[i],&z[i]);
        if (i<n) in[i]=1,addedge(i); else E.push_back({z[i],i});
    }
    sort(E.begin(),E.end());
    for (auto [_,id]:E)
    {
        if (in[id]) continue;
        for (RI i=1;i<=n;++i) pre[i]=0; pre[x[id]]=-1;
        find_path(x[id]); pi mx={0,0};
        for (int now=y[id];now!=x[id];now=pre[now]) mx=max(mx,lst[now]);
        if (mx.fi>z[id])
        {
            ans.push_back({id,mx.se});
            deledge(mx.se); in[mx.se]=0;
            addedge(id); in[id]=1;
        }
    }
    printf("%d\n",ans.size());
    for (auto [x,y]:ans) printf("%d %d\n",x,y);
    return 0;
}