#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define all(x) x.begin(), x.end()
#define pb push_back
#define f first
#define s second

const int MX = 3005;

#define FOR(i,a,b) for(int i=a;i<b;i++)
#define For(i,a) FOR(i,0,a)
#define pi pair<int,int>
#define trav(a,b) for(auto& a:b)

vector<pair<pi,int>> adj[MX];
pair<pi,int> adj2[MX];
int n,m;

int findInd(unordered_set<int>& cmp) {
    For(i,n-1) {
        int u = adj2[i].f.f;
        int v=adj2[i].f.s;
        if(cmp.count(u) ^ cmp.count(v)) {
            return i;
        }
    }
    assert(false);
    return -1;
}


int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    if (fopen("input.in", "r")) {
        freopen("input.in", "r", stdin);
        freopen("output.out", "w", stdout);
    }
    unordered_set<int> cmp;
    vector<pi> ans;
    set<pair<pi,int>> avail;
    cin>>n>>m;
    For(i,m) {
        int u,v,w;cin>>u>>v>>w;
        u--;v--;
        adj[u].pb({{w,i},v});
        adj2[i]={{u,v},w};
    }

    cmp.insert(0);
    trav(x,adj[0]){
        avail.insert(x);
    }
    For(i,n-1) {
        while(true) {
            assert(avail.size());
            auto x = *avail.begin();
            int w = x.f.f, ind = x.f.s, v = x.s;
            avail.erase(avail.begin());
            if(cmp.count(v)) {
                continue;
            }

            if(ind >=n-1) {
                ans.pb({findInd(cmp), ind});
            }

            cmp.insert(v);
            trav(x,adj[v]) {
                avail.insert(x);
            }
            break;
        }
    }

    cout << ans.size() << '\n';
    trav(x,ans) {
        cout << x.f+1 << " " << x.s+1 << '\n';
    }
    cout << endl;


    

}