#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define data dataa
using LL=long long;
using ULL=unsigned long long;
using LD=long double;
const int N=2010;
const int M=3010;
vector<pair<int,int>>ans,g[N];
struct EDGE{int x,y,w,id;}edge[M];
int n,m,u[M],v[M],weight[M],fa[N],fid[N];
set<int>s;
void dfs(int p)
{
    for(auto [x,y]:g[p])
    {
        if(x==fa[p])continue;
        fa[x]=p;fid[x]=y;
        dfs(x);
    }
}
int main()
{
    scanf("%d%d",&n,&m);
    rep(i,m)
    {
        int x,y,w;
        scanf("%d%d%d",&x,&y,&w);
        edge[i]={x,y,w,i};
        u[i]=x;v[i]=y;weight[i]=w;
    }
    rep(i,n-1)s.insert(i);
    sort(edge+1,edge+m+1,[&](const EDGE&x,const EDGE&y){return x.w<y.w;});
    rep(i,m)
    {
        int x=edge[i].x,y=edge[i].y,w=edge[i].w,id=edge[i].id;
        if(s.contains(id))continue;
        rep(j,n)g[j].clear();
        for(auto j:s)g[u[j]].pb(mp(v[j],j)),g[v[j]].pb(mp(u[j],j));
        fa[x]=0;
        dfs(x);
        int pos=-1,mx=0;
        for(;y!=x;y=fa[y])if(weight[fid[y]]>mx)mx=weight[fid[y]],pos=fid[y];
        if(weight[pos]>w)
        {
            ans.pb(mp(pos,id));
            s.erase(pos);
            s.insert(id);
        }
    }
    printf("%d\n",int(ans.size()));
    for(auto [x,y]:ans)printf("%d %d\n",x,y);
    return 0;
}