#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'

class dsu {
    public:
    vector<int> p, sz;
    int n, groups;
    dsu(int _n) : n(_n), groups(_n) {
	    p.resize(n);
	    iota(p.begin(), p.end(), 0);
	    sz.assign(n,1);
    }
    int get(int x) {
        return (x == p[x] ? x : (p[x] = get(p[x])));
    }
    bool unite(int x, int y) {
        x = get(x);
        y = get(y);
        if (x != y) {
        	if(sz[x] < sz[y]) swap(x,y);
            p[y] = x;
            sz[x] += sz[y];
            groups--;
            return true;
        }
        return false;
    }
    int size(int x){
    	return sz[get(x)];
    }
};

int main(){
	ios::sync_with_stdio(false); cin.tie(0);
	int n, m;
	cin >> n >> m;
	dsu d(n);
	vector<array<int,4>> a(m);
	for(int i=0; i<m; i++){
	    cin >> a[i][2] >> a[i][3] >> a[i][0];
	    a[i][2]--;
	    a[i][3]--;
	    a[i][1] = i;
	}
	sort(a.begin(), a.end());
	vector<int> res(m);
	for(auto &[_, idx, u, v] : a){
	    if(d.get(u) != d.get(v)){
	        res[idx] = 1;
	        // cout << "use " << idx << endl;
	        d.unite(u, v);
	    }
	}
	vector<int> rmv, add;
	for(int i=0; i<m; i++){
	    if(res[i] && i>=n-1) add.push_back(i);
	    if(!res[i] && i<n-1) rmv.push_back(i);
	}
	assert(add.size() == rmv.size());
	cout << add.size() << endl;
	for(int i=0; i<add.size(); i++){
	    cout << rmv[i]+1 << ' ' << add[i]+1 << endl;
	}
}