#include<bits/stdc++.h>

using namespace std;
 
typedef long long int ll;
typedef long double ld;
#define f first
#define s second
#define pb push_back
#define pii pair<int, int>

 
const int N = 1e5 + 100;
const int inf = 1e9;
const ll mod =  9302023;


int par[N], rk[N], pr[N], ind_p[N], W[N];
int n, m, X[N], Y[N];
vector<pii> adj[N], ans;
bool mark[N];
vector<pair<pii, pii>> e;


int find_par(int x)
{
	if(x == par[x])
		return x;
	return par[x] = find_par(par[x]);	
}

void dfs(int u)
{
	for(auto v : adj[u])
	{
		if(v.f != pr[u])
		{
			pr[v.f] = u;
			ind_p[v.f] = v.s;
			dfs(v.f);
		}
	}
}



void build()
{
	for(int i = 0; i < n; i++)
		adj[i].clear();
	for(int i = 0; i < m; i++)
	{
		pr[i] = -1;
		if(mark[i])
		{
			adj[X[i]].pb({Y[i], i});
			adj[Y[i]].pb({X[i], i});
		}
	}
}

void merge(int x, int y, int w, int ind)
{
	int u = x, v = y;
	x = find_par(x);
	y = find_par(y);
	if(x == y)
		return;
	
	if(!mark[ind])
	{
		//cout << ind << endl;
		build();
		dfs(u);
		while(pr[v] != -1)
		{
			if(W[ind_p[v]] > w)
			{
				ans.pb({ind_p[v], ind});
				mark[ind] = 1;
				mark[ind_p[v]] = 0;
				break;
			}
			v = pr[v];
		}
				
	}	
	
	if(rk[x] < rk[y])
		swap(x, y);
	par[y] = x;
	if(rk[x] == rk[y])
		rk[x]++;	
}


int main()
{
	
	cin >> n >> m;
	for(int i = 0; i < n; i++)
	{
		par[i] = i;
	}
	for(int i = 0; i < m; i++)
	{
		int x, y, w;
		cin >> x >> y >> w;
		x--; y--;
		W[i] = w;
		X[i] = x;
		Y[i] = y;
		if(i < n-1)
		{
			mark[i] = 1;
		}
		
		e.pb({{w, i}, {x, y}});
	}
	
	
	sort(e.begin(), e.end());	
	for(auto it : e)
		merge(it.s.f, it.s.s, it.f.f, it.f.s);
		
		
	cout << ans.size() << endl;
	for(auto it : ans)
		cout << it.f + 1 << ' ' << it.s + 1 << endl;		
			
    return 0;
}